Image reading apparatus

ABSTRACT

An image reading apparatus having a high-contrast mode of operation for reading character images and a halftone mode of operation for reading halftone images, including an image sensor converting optical image information into electric signals, an optical system for projecting an image on a document onto the image sensor, a threshold signal generator capable of generating a plurality of first threshold signals and operative to output one of the first threshold signals, a threshold signal generator capable of generating a plurality of second threshold signals and operative to output one of the second threshold signals, a mode selector circuit for selecting the high-contrast or halftone mode of operation, a density selector circuit for selecting the first threshold signal during the high-contrast mode of operation and the second threshold signal during the halftone mode of operation, and a combination of circuit networks for outputting halftone image signals during the high-contrast mode of operation on the basis of the electric signals from the image sensor and the first threshold signal from the first threshold signal generator and outputting high-contrast image signals during the halftone mode of operation on the basis of the electric signals from the image sensor and the second threshold signal from the second threshold signal generator.

This application is a continuation of application Ser. No. 07/375,728,filed Jul. 5, 1989 now U.S. Pat. No. 5,079,638.

FIELD OF THE INVENTION

The present invention relates to an image reading apparatus and, moreparticularly, to an image reading apparatus of the type in which opticalimage information picked up from an image-carrying document is projectedonto an array of photoelectric transducers for conversion into electricsignals representative of the image on the document and processing theelectric signals to generate binary signals representing the image to bereproduced.

BACKGROUND OF THE INVENTION

In a known image reading apparatus of the described type, optical imageinformation picked up from an image-carrying document is projected ontoan array of photoelectric transducers for producing analog electricsignals representative of the image on the document. These analogelectric signals representing the image on the original document areconverted into digital signals by means of an analog-to-digitalconverter. The digital signals thus generated are supplied to acomparator circuit for comparison with a reference signal indicative ofa predetermined image density for thereby producing binary signalsrepresenting the image to be reproduced.

As the reference signal used in producing the binary signals from thedigital signals output from the analog-to-digital converter may utilizeeither a signal corresponding to a fixed image density or a signalstepwise variable within a predetermined range in accordance with aprescribed rule formulated by a "dither" pattern of the signal valuesdictating the stepwise variation of the reference signal. The formermanner of producing the binary signals is known as the simplebinarization mode and is frequently used for the reproduction ofhigh-contrast images such as typically character images or images mostlycomposed of linear features. The latter manner of producing the binarysignals is known as the halftone mode and is frequently used for thereproduction of halftone images such as typically photographic orpictorial images.

In the meantime, a known image reading apparatus of the described typehas capabilities to adjust the density with which the images picked upfrom a document are to be reproduced. Such capabilities are useful forthe reproduction of images clearly without respect to the densitydistribution of the original images on the document. The image readingapparatus having the density adjusting capabilities may have anautomatic density control mode for automatically adjusting the densityof the images to be reproduced, and a manual density control modeallowing the user of the apparatus to manually select the density of theimages.

A conventional image reading apparatus having the automatic and manualdensity adjusting functions is however not fully acceptable for clearlyreproducing images on a document having both character images andphotographic or pictorial features or, in general, a document havingirregular density distribution.

SUMMARY OF THE INVENTION

It is, accordingly, an important object of the present invention toprovide an improved image reading apparatus which is capable of clearlyreproducing images on a document.

It is another important object of the present invention to provide animproved image reading apparatus which will make it possible toreproduce images on a document clearly without respect to the densitydistribution of the original images on the document.

It is still another important object of the present invention to providean improved image reading apparatus capable of clearly reproducingimages on a document having irregular density distribution.

It is still another important object of the present invention to providean improved image reading apparatus capable of clearly reproducingimages on a document having both character images and photographic orpictorial features.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of an image reading apparatus according tothe present invention will be more clearly appreciated from thefollowing description taken in conjunction with the accompanyingdrawings which show various preferred embodiments of an image readingapparatus according to the drawings. In the invention:

FIG. 1 is a side elevation view showing the general arrangement of animage reading apparatus forming each of the preferred embodiments of animage reading apparatus according to the present invention,particularly, an optical image scanning and image sensing systemsforming part of the apparatus;

FIG. 2 is a plan view showing the key/indicator configuration of acontrol panel included in a first preferred embodiment of an imagereading apparatus according to the present invention;

FIGS. 3A to 3C are diagrams showing the basic principles on which theoriginal density levels of pixels forming a frame of image are to bebinarized in reading the image in the simple binarization mode of imagereading operation, wherein FIG. 3A shows the distribution of theoriginal pixel densities indicated by digital data in hexadecimalnotation, FIG. 3B shows examples of a fixed threshold value which may beused in binarizing the original pixel densities, and FIG. 3C shows thedistribution of the binarized densities of the pixels having theiroriginal density levels indicated by the digital data illustrated inFIG. 3A;

FIG. 4 is a diagram showing the basic principles on which the originaldensity levels of pixels forming a frame of image are to be binarized inreading the image in the halftone mode of image reading operation usinga set of threshold values;

FIG. 5 is a diagram showing examples of a group of conceptual thresholdvalues used in binarizing the original pixel densities in relation topredetermined representatives of the density distribution of the entirepixel matrix;

FIGS. 6A to 6C are diagrams similar to FIGS. 3A to 3C but now show thebasic principles on which the original density levels of pixels forminga frame of image are to be binarized with use of a group of conceptualthreshold values in relation to a plurality of values representing thedensity distribution of the pixel matrix in reading the image in thehalftone mode of image reading operation, wherein FIG. 6A shows theoriginal density levels of the pixels indicated by digital dataexpressed in hexadecimal notation, FIG. 6B shows examples of the groupsof conceptual threshold values which may be used in relation to valuesrepresenting the density distribution of the pixel matrix in binarizingthe original pixel densities, and FIG. 6C shows the distribution of thebinarized densities of the pixels having their original density levelsindicated by the digital data illustrated in FIG. 6A;

FIG. 7 is a diagram showing the distribution of the pixel densities of aframe of image detected from a character document having no halftoneimage area, the densities being expressed in hexadecimal notation.

FIG. 8 is a diagram showing the distribution of the pixel densities of aframe of image picked up from a photographic document, the densitiesbeing also expressed in hexadecimal notation;

FIG. 9 is a block diagram showing the general construction andarrangement of a control circuit for use in the first preferredembodiment of an image reading apparatus according to the presentinvention;

FIG. 10 is a flowchart showing a main routine program to be executed bythe central processing unit included in the control circuit illustratedin FIG. 9;

FIG. 11 is a flowchart showing the details of a mode shift subroutineprogram included in the main routine program illustrated in FIG. 10;

FIGS. 12A and 12B are flowcharts showing the details of an image readcontrol subroutine program further included in the main routine programillustrated in FIG. 10;

FIG. 13 is a perspective view showing the key and tablet configurationof an editor module forming part of a second preferred embodiment of animage reading apparatus according to the present invention;

FIG. 14 is a plan view similar to FIG. 2 but now shows the key/indicatorconfiguration of a control panel further included in the secondpreferred embodiment of an image reading apparatus according to thepresent invention;

FIG. 15 is a block diagram similar to FIG. 9 but now shows the generalconstruction and arrangement of a control circuit for use in the secondpreferred embodiment of an image reading apparatus according to thepresent invention;

FIG. 16 is a flowchart showing a main routine program to be executed bythe central processing unit included in the control circuit illustratedin FIG. 15;

FIG. 17 is a flowchart showing the details of a mode shift subroutineprogram included in the main routine program illustrated in FIG. 16;

FIG. 18 is a flowchart showing the details of an attribute designationcontrol subroutine program also included in the main routine programillustrated in FIG. 16;

FIGS. 19A and 19B are flowcharts showing the details of an image readcontrol subroutine program further included in the main routine programillustrated in FIG. 16;

FIG. 20 is a perspective view showing the key and tablet configurationof an editor module forming part of a third preferred embodiment of animage reading apparatus according to the present invention;

FIG. 21 is a block diagram similar to FIG. 15 but now shows the generalconstruction and arrangement of a control circuit for use in the thirdpreferred embodiment of an image reading apparatus according to thepresent invention;

FIG. 22 is a flowchart showing a main routine program to be executed bythe central processing unit included in the control circuit illustratedin FIG. 21;

FIG. 23 is a flowchart showing the details of a mode shift subroutineprogram included in the main routine program illustrated in FIG. 22;

FIG. 24 is a flowchart showing the details of an area attributedesignation control subroutine program also included in the main routineprogram illustrated in FIG. 16;

FIG. 25 is a plan view showing the key/indicator configuration of acontrol panel further included in a fourth preferred embodiment of animage reading apparatus according to the present invention;

FIG. 26 is a perspective view showing the key and tablet configurationof an editor module forming part of the fourth preferred embodiment ofan image reading apparatus according to the present invention;

FIG. 27 is a block diagram similar to FIG. 15 but now shows the generalconstruction and arrangement of a control circuit for use in the fourthpreferred embodiment of an image reading apparatus according to thepresent invention;

FIG. 28 is a flowchart showing a main routine program to be executed bythe central processing unit included in the control circuit illustratedin FIG. 27;

FIG. 29 is a flowchart showing the details of a mode shift subroutineprogram included in the main routine program illustrated in FIG. 28;

FIG. 30 is a flowchart showing the details of an area attributedesignation control subroutine program also included in the main routineprogram illustrated in FIG. 28;

FIG. 31 is a flowchart showing the details of an image read controlsubroutine program further included in the main routine programillustrated in FIG. 28;

FIGS. 32A and 32B are flowcharts showing the details of a preliminaryscan control subroutine program included in the image read controlroutine program illustrated in FIG. 31;

FIGS. 33A and 33B are flowcharts showing the details of a regular scancontrol subroutine program also included in the image read controlroutine program illustrated in FIG. 31;

FIG. 34 is similar to FIGS. 3A to 3C, respectively, but shows the basicprinciples on which the original density levels of pixels forming aframe of image in a character document having a relatively lightbackground area may be binarized in the simple binarization mode ofimage reading operation in the preliminary scan control subroutineprogram illustrated in FIG. 32 with use of a relatively low firstthreshold value to produce the binarized densities of the pixels;

FIG. 35 is a diagram similar to FIG. 7 but shows the distribution of thepixel densities of the frame of image which has the original densitylevels shown in FIG. 34 and which is to be binarized with use of therelatively low first threshold value shown in FIG. 34;

FIG. 36 is similar to FIG. 34, but shows the basic principles on whichthe original density levels of pixels forming a frame of image in acharacter document having a relatively dark background area may bebinarized in the simple binarization mode of image reading operation inthe preliminary scan control subroutine program illustrated in FIG. 32with use of a relatively high second threshold value to produce thebinarized densities of the pixels;

FIG. 37 is a diagram similar to FIG. 35 but shows the distribution ofthe pixel densities of the frame of image which has the original densitylevels shown in FIG. 36 and which is to be binarized with use of therelatively high second threshold value shown in FIG. 36;

FIG. 38 is similar to FIGS. 6A to 6C, respectively, but shows the basicprinciples on which the original density levels of pixels forming aframe of image in a photographic document having a relatively lightbackground area may be binarized in the halftone mode of image readingoperation in the preliminary scan control subroutine program illustratedin FIG. 32 with use of a relatively low first set of threshold values toproduce the binarized densities of the pixels;

FIG. 39 is a diagram similar to FIG. 8 but shows the distribution of thepixel densities of the frame of image which has the original densitylevels shown in FIG. 38 and which is to be binarized with use of therelatively low first threshold value shown in FIG. 38;

FIG. 40 is similar to FIG. 38, but shows the basic principles on whichthe original density levels of pixels forming a frame of image in aphotographic document having a relatively dark background area may bebinarized in the halftone mode of image reading operation in thepreliminary scan control subroutine program illustrated in FIG. 32 withuse of a relatively high second set of threshold values to produce thebinarized densities of the pixels;

FIG. 41 is a diagram similar to FIG. 39 but shows the distribution ofthe pixel densities of the frame of image which has the original densitylevels shown in FIG. 40 and which is to be binarized with use of therelatively high second set of threshold values shown in FIG. 40;

FIG. 42 is a diagram showing the input-output characteristics of a groupof conceptual threshold values, viz., the relationship between theoriginal image densities of a document scanned and the image densitiesbinarized on the principles indicated in FIG. 38;

FIG. 43 is a diagram showing an example of the dither pattern which maybe used to provide the input-output characteristics indicated in FIG.42;

FIG. 44 is a diagram similar to FIG. 42 but shows the the relationshipbetween the original image densities of a document scanned and the imagedensities binarized on the principles indicated in FIG. 40;

FIG. 45 is a diagram similar to FIG. 42 but shows an example of thedither pattern which may be used to provide the input-outputcharacteristics indicated in FIG. 44;

FIG. 46 is a block diagram similar to FIG. 27 but now shows the generalconstruction and arrangement of a control circuit for use in the fifthpreferred embodiment of an image reading apparatus according to thepresent invention;

FIG. 47 is a block diagram showing the detailed construction of theimage sensor included in the control circuit illustrated in FIG. 46;

FIG. 48 is a block diagram showing the arrangement of ananalog-to-digital converter and a converter reference voltage generatorwhich also form part of the control circuit illustrated in FIG. 46;

FIG. 49 is a graphic representation of the variation in the voltage ofan analog image density data signal output from each of the individualelements of the CCD array forming part of the image sensor included inthe control circuit illustrated in FIG. 46;

FIG. 50 is a view showing a graphic representation of a digital imagedensity data signal which may be converted from the analog image densitydata signal indicated in FIG. 49;

FIG. 51 shows diagrams showing the basic principles on which theoriginal density levels of pixels forming a frame of image are to bebinarized with different sets of reference voltage signals for theanalog-to-digital converter in the control circuit illustrated in FIG.46, thus showing examples of the signals involved in the operation ofthe analog-to-digital converter;

FIGS. 52A and 52B are flowcharts showing the details of a preliminaryscan control subroutine program to be executed by the central processingunit included in the control circuit illustrated in FIG. 46;

FIGS. 53A to 53E are diagrams showing the basic principles on whichbinarized image density data signals are to be produced from analogimage density data signals with standard reference voltage signalsapplied to the analog-to-digital converter during simple binarizationmode of image reading operation;

FIGS. 54 shows diagrams showing the basic principles on which binarizedimage density data signals are to be produced from analog image densitydata signals with modified reference voltage signals applied to theanalog-to-digital converter during simple binarization mode of imagereading operation;

FIG. 55 shows diagrams showing the basic principles on which binarizedimage density data signals are to be produced from analog image densitydata signals with standard reference voltage signals applied to theanalog-to-digital converter during halftone mode of image readingoperation;

FIG. 56 shows diagrams showing the basic principles on which binarizedimage density data signals are to be produced from analog image densitydata signals with modified reference voltage signals applied to theanalog-to-digital converter during halftone mode of image readingoperation;

FIG. 57 is a perspective view showing the key and tablet configurationof an editor module forming part of a sixth preferred embodiment of animage reading apparatus according to the present invention;

FIG. 58 is a plan view showing the key/indicator configuration of acontrol panel further included in the sixth preferred embodiment of animage reading apparatus according to the present invention;

FIG. 59 is a block diagram showing the general construction andarrangement of a control circuit for use in the fourth preferredembodiment of an image reading apparatus according to the presentinvention;

FIG. 60 is a flowchart showing a main routine program to be executed bythe central processing unit included in the control circuit illustratedin FIG. 59;

FIG. 61 is a flowchart showing the details of a mode shift subroutineprogram included in the main routine program illustrated in FIG. 60;

FIG. 62 is a flowchart showing the details of an area attributedesignation control subroutine program also included in the main routineprogram illustrated in FIG. 60;

FIGS. 63A and 63B are flowcharts showing the details of a preliminaryscan control subroutine program included in the main routine programillustrated in FIG. 60;

FIGS. 64A and 64B are flowcharts showing the details of a regular scancontrol subroutine program also included in the main routine programillustrated in FIG. 60;

FIG. 65 is a block diagram similar to FIG. 59 but now shows the generalconstruction and arrangement of a control circuit for use in a seventhpreferred embodiment of an image reading apparatus according to thepresent invention; and

FIG. 66A and 66B are flowcharts showing the details of a preliminaryscan control subroutine program included in the image read controlroutine program illustrated in FIG. 65.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various preferred embodiment of an image reading apparatus according tothe present invention will be hereinafter described with reference tothe drawings. These preferred embodiments of the present invention areassumed, for purposes of description, as being generally similar inhardware construction. FIG. 1 shows the general arrangement of an imagereading apparatus forming each of such preferred embodiment of thepresent invention, particularly, an optical image scanning system whichforms part of the apparatus. The image reading apparatus herein shownmay be part of an image duplicating apparatus adapted to reproduce aprinted duplicate of an original image-carrying medium which is hereinreferred to as document.

Referring to FIG. 1, the image reading apparatus embodying the presentinvention comprises a housing structure 100 having a horizontal upperpanel which is in part formed by a transparent document support table102 of, typically, glass. On this document support table 102 of glass isto be placed an image-carrying document D to be duplicated. The positionof the document D thus placed on the document support table 102 isindicated by a document scale 104 arranged on the upper panel of thehousing structure 100. The document scale 104 has a lower face havingimprinted thereon graphic patterns including a focus adjusting pattern,a reduction/magnification ratio detecting pattern, and a shading datacorrecting pattern, though not shown in the drawings. The document Dplaced on the document support table 102 is held in position and isshielded from external light by means of a suitable lid member hingedlyconnected to the housing structure 100, though not shown in thedrawings.

The optical image scanning system of the apparatus embodying the presentinvention comprises a source of light typically implemented by a halogenexposure lamp 106 located immediately underneath the document supporttable 102, and a concave reflector mirror 108 located in conjunctionwith the exposure lamp 106 so that the light emanating from the lamp isdirected in major proportion toward the lower face of the documentsupport table 102. The light thus directed toward the lower face of thedocument support table 102 is reflected from the lower image-carryingface of the document D placed on the table 102 and the resultantimage-bearing beam of light B is directed and re-directed successivelyby means of first, second and third plane reflector mirrors 110, 112 and114 to horizontally advance toward a lens/sensor assembly 116.

The exposure lamp 106, concave reflector mirror 108 and first planereflector mirror 110 are supported in combination on a commonlamp/mirror carrier 118 which is horizontally movable back and forthalong the document support table 102 as indicated by arrowheads a anda'. In addition, the second and third plane reflectors 112 and 114 arejointly supported on a common mirror carrier 120 which is alsohorizontally movable back and forth along the document support table 102as indicated by arrowheads b and b'. Though not shown in the drawings,suitable detecting means is provided in association with each of thelamp/mirror carrier 118 and mirror carrier 120 to detect if theassociated carrier is in a predetermined home position with respect tothe document support table 102.

The lens/sensor assembly 116 comprises a lens unit 122 and a sensor unit124 mounted on a common lens/sensor carrier 126 which is movable backand forth in parallel with the path of light advancing from the thirdplane reflector mirror 114, as indicated by arrowheads c and c'. Theimage-bearing beam of light B reflected from the third plane reflectormirror 114 is thus passed through the lens unit 122 to the sensor unit124. The sensor unit 124 comprises a photosensitive image sensor 128which is mounted on a sensor holder 130 supported on the lens/sensorcarrier 126. The photosensitive image sensor 128 is implemented by anarray of photoelectric transducers such as typically semiconductorcharge-coupled devices (CCD's) and is operative to generate a set ofelectric signals responsive to the image information contained in theimage-bearing beam B incident on the array of the charge-coupleddevices. The sensor holder 130 is movable back and forth on thelens/sensor carrier 126 in parallel with the path of light entering thelens/sensor assembly 120, as indicated by arrowheads d and d'.

Drive means are provided to drive each of the carriers 118, 120 and 126for movement. These drive means include a reversible scanner drive motor132 (M1) for driving each of the lamp/mirror carrier 118 and mirrorcarrier 120. This scanner drive motor 132 is operatively coupled to thelamp/mirror and mirror carriers 118 and 120 through suitable reductiongear or belt and pulley arrangement (not shown) so that the mirrorcarrier 120 carrying the mirrors 112 and 114 is to be driven formovement at a speed equal to one half of the speed at which thelamp/lens carrier 118 carrying the lamp 106 and mirrors 108 and 110 isdriven for movement.

The drive means further include a reversible lens/sensor drive motor 134(M2) for driving the lens/sensor carrier 126. This lens/sensor drivemotor 134 is to be actuated into operation to adjust the imagereduction/magnification ratio by movement of the lens unit 122 in thedirection of arrowhead c or in the direction of arrowhead c'. The sensorholder 130 is driven for movement on the lens/sensor carrier 126 in thedirection of the arrowhead d or in the direction of arrowhead and d' bymeans of a sensor drive motor 136 (M3). Immediately after the apparatusis switched in, the sensor drive motor 136 is actuated into operation sothat the image picked up from the focus adjusting pattern imprinted onthe lower face of the document scale 104 as has been noted is correctlyfocussed on the array of the charge-coupled devices forming the imagesensor 128.

First Preferred Embodiment (FIGS. 2 to 12)

FIG. 2 shows the key/indicator configuration of a control panel 140Awhich forms part of a first preferred embodiment of an image readingapparatus according to the present invention. On the control panel 140Aare provided a scan start key 142 (labelled "SCAN") to be used to enteran instruction to start a cycle of operation to scan a document D placedon the document support table 102, viz., read the image information onthe document D placed on the table 102,

a common clear key 144 (labelled "C") to be used to enter an instructionto clear or cancel a command which has once been entered to select anydesired mode of operation,

a four-digit eight-segment numerical display section 146 for indicatingthe reduction/magnification ratio detected from thereduction/magnification ratio detecting pattern on the lower face of thedocument scale 104,

an image scale-up key 148 (labelled "+") to be used to enter aninstruction to increase the valid reduction/magnification ratio forimage reproduction,

an image scale-down key 150 (labelled "-") to be used to enter aninstruction to increase the valid reduction/magnification ratio forimage reproduction,

a sheet size indicator section 152 which consists of a plurality ofsubsections for indicating different standardized sizes, respectively,of print output sheets such as the subsection 152a for indicating thestandard A4 size in longitudinal as shown highlighted,

a first sheet size select key 154 (labelled "+") used to move highlightthrough the subsections of the indicator section 152 in one direction toselect any of the print output sheet sizes indicated by the subsections,

a second sheet size select key 156 (labelled "-") used to move highlightthrough the subsections of the indicator section 152 in the oppositedirection to select any of the print output sheet sizes indicated by thesubsections,

a simple binarization or "character" mode select key 158 (labelled"CHARAC") to be used to enter an instruction to select a simplebinarization mode of image reading operation,

a halftone mode select key 160 (labelled "H/T") to be used to enter aninstruction to select a halftone mode of image reading operation,

a density indicator section 162 consisting of a series of subsectionsarranged in the order of lightness indicated by letters "D" (dark), "M"(medium) and "L" (light) for the simple binarization mode and bynumerals "1" to "9" for the halftone mode, the selected density forimage reading being shown highlighted such as the density "D" for thesimple binarization mode and the density "4" for the halftone mode,

a density "plus" key 164 (labelled "+") used to enter an instruction toincrease the valid degree of lightness for image reading, and

a density "minus" key 166 (labelled "-") used to enter an instruction todecrease the valid degree of lightness for image reading.

FIGS. 3A to 3C show the basic principles on which the original densitylevels of pixels forming a frame of image on an image-carrying documentare to be binarized in reading the image in the simple binarization modeof image reading operation. The original density level of each pixel ofthe matrix is given by digital data expressed in hexadecimal notationand is digitally variable from 00 to FF(H) (=255 in decimal) as shown inFIG. 3A. The original pixel density of zero level indicates pure whiteand the original pixel density of the FF(H) level indicates pure black.For purposes of discussion, it is herein assumed that the originaldensity levels of the individual pixels forming the matrix are binarizedwith use of a first threshold value T_(A) indicated by broken lines inFIG. 3B or a second threshold value T_(B) larger than the firstthreshold value T_(A) as indicated by full lines in FIG. 3B.

FIG. 3C shows the distribution of the binarized densities of the pixelshaving their original density levels indicated by the digital dataillustrated in FIG. 3A. As will be seen from FIG. 3C, the original pixeldensities lower than the threshold value T_(A) or T_(B) are binarized asthe density represented by logic "0" value, while the original pixeldensities higher than the threshold value T_(A) or T_(B) are binarizedas the density represented by logic "1" value.

It will be further seen from FIG. 3C that, where the relatively lowthreshold value T_(A) is used for the simple binarization mode of imagereading operation, the original densities of the pixels are likely to bebinarized as the density of logic "1" value rather than as the densityof logic "0" value. On the contrary, where the relatively high thresholdvalue T_(B) is used for the simple binarization mode of image readingoperation, the original pixel densities are likely to be binarized asthe density of logic "0" value rather than as the density of logic "1"value. These mean that a frame of image reproduced in the simplebinarization mode of image reading operation using the lower thresholdvalue T_(A) will appear darker in its entirety than a frame of imagereproduced in the simple binarization mode of image reading operationusing the higher threshold value T_(B).

The second threshold value T_(B) is higher by a certain value than thefirst threshold value T_(A) so that, where the first threshold valueT_(A) is once given, the second threshold value T_(B) will be givenautomatically when a predetermined value is added to the first thresholdvalue T_(A). This means that the density of a frame of image reproducedin the simple binarization mode of image reading operation can beadjusted through addition of a desired value to (or through deduction ofa desired value from) the preliminarily given "basic" threshold valuewhich is herein represented by the first threshold value T_(A).

Description will now be made in regard to the basic principles on whichthe original density levels of pixels forming a frame of image on animage-carrying document are to be binarized in reading the image in thehalftone mode of image reading operation. As well known in the art, athreshold value used in the halftone is given in the form of a ditherpattern or, in other words, a set of threshold values falling within apredetermined range, as represented by a first set of threshold valuesT_(GA) indicated by a vertically hatched area in FIG. 4 or a second setof threshold values T_(GB) indicated by a horizontally hatched area inFIG. 4. In the description to follow, it is assumed that a set ofthreshold values such as the set of threshold values T_(GA) or T_(GB)shown in FIG. 4 has a representative which may be given by the median,mean or mode of the threshold values. It is herein further assumed thata matrix of pixels having their original density levels represented bydigital data has its density distribution represented by a plurality ofrepresentatives.

When a value representing the density distribution of the pixel matrixis larger than the representative of the set of threshold values such asthe set of threshold values T_(GA) shown in FIG. 4, the originaldensities of the pixels are likely to be binarized as densitiesindicating black rather than white and, thus, the frame of imagereproduced in the halftone mode of image reading operation using the setof such threshold values will appear dark or "blackish" rather thanlight or "whitish". On the contrary, the original densities of pixelsforming a frame of image are likely to be binarized as densitiesindicating white rather than black and the frame of image reproduced inthe halftone mode of image reading operation using the set of suchthreshold values will appear light or "whitish" rather than dark or"blackish" when a value representing the density distribution of thepixel matrix is less than the representative of the set of thresholdvalues.

For purposes of description, the degree of "whitishness" and the degreeof "blackishness" of a frame of image or a matrix of pixels forming theframe of image are herein defined through introduction of a group ofconceptual threshold values in relation to the representative of thedensity distribution of the pixel matrix. A group of conceptualthreshold values is expressed by a predetermined linear or curvilinearplot varying between predetermined lower and upper limit thresholdvalues which correspond to the densities indicating pure white and pureblack, respectively, as indicated by plots T_(CGA) and T_(CGB) in FIG.5.

FIGS. 6A to 6C show the basic principles on which the original densitylevels of pixels forming a frame of image in the form of a pixel matrixare to be modified with use of a group of conceptual threshold values inrelation to a plurality of values representing the density distributionof the pixel matrix in reading the image in the halftone mode of imagereading operation. The original density level of each pixel of thematrix is also given by digital data expressed in hexadecimal notationand is digitally variable from 00 to FF(H) as shown in FIG. 6A. Theoriginal density levels of the individual pixels forming the matrix aremodified with use of a first group of conceptual threshold valuesT_(CGA) indicated by broken lines in FIG. 6B or a second group ofconceptual threshold values T_(CGB) indicated by full lines in FIG. 6B.The first group pf conceptual threshold values T_(CGA) is defined to behigher in its entirety than the second group of conceptual thresholdvalues T_(CGB). Used as the values representing the density distributionof the pixel matrix include three different values D_(R1), D_(R2) andD_(R3) which are larger in this sequence between the values representingpure white and pure black.

FIG. 6C shows the distribution of the modified densities of the pixelshaving their original density levels indicated by the digital dataillustrated in FIG. 6A. As will be seen from FIG. 6C, the original pixeldensities lower than the group of conceptual threshold values T_(CGA) orT_(CGB) are modified into any of five values. These modified densityvalues consist of a value ("W") corresponding to the original pixeldensities less than the first representative value D_(R1), a valuecorresponding to the original pixel densities between the first andsecond representative values D_(R1) and D_(R2), a value ("G")corresponding to the original pixel densities between the second andthird representative values D_(R2) and D_(R3), and a value ("B")corresponding to the original pixel densities larger than the thirdrepresentative value D_(R3).

It will be seen from FIG. 6C that, when the group of relatively lowconceptual threshold values T_(CGA) is used in relation to thepredetermined representatives of the original pixel densities, theoriginal pixel densities are likely to be modified into values effectiveto reproduce a frame of image which will in its entirety appear darkeror more "blackish" than a frame of image reproduced with use of thegroup of relatively high conceptual threshold values T_(CGB) in relationto the same representatives of the original pixel densities. This meansthat the density of a frame of image reproduced in the halftone mode ofimage reading operation can also be adjusted through addition of adesired value to (or through deduction of a desired value from) thepreliminarily given "basic" set of threshold values which is hereinrepresented by the first set of threshold values T_(GA).

FIG. 7 shows the distribution of the pixel densities of a frame of imagedetected from a document having no halftone image area, the densitiesbeing expressed in hexadecimal notation. As will be seen from the curveindicated in FIG. 7, the frequencies with which the pixel densities of aframe of image having no halftone image area occur have two peak zonesP_(C) and P_(B), one zone P_(C) corresponding to the areas (hereinreferred to as character areas) occupied by characters and the otherzone P_(B) corresponding to the areas (herein referred to as backgroundareas) surrounding the character areas of the image frame. The densitiesof the pixels forming a frame image on this type of document(hereinafter referred to as character document) can be binarizedadvantageously in the simple binarization mode of image readingoperation. The threshold value for use in this simple binarization modeof image reading operation is preferably selected to intervene betweenthe maximum density P_(Cmax) of the lower-density or background-areapeak zone P_(C) and the minimum density P_(Cmin) of the higher-densityor character-area peak zone P_(B). The use of such a threshold valuewill prove advantageous for precluding the fading of characters in thecharacter areas and the production of fogging in the background areas ofthe document.

It may be further noted that, for the binarization of the pixeldensities of a frame of image on a character document, it is of no useto minutely vary the threshold because of the fact that there could beno pixel densities which intervene between the maximum density P_(Cmax)of the background-area peak zone P_(C) and the minimum density P_(Cmin)of the character-area peak zone P_(B). In the first preferred embodimentof a image reading apparatus according to the present invention, it isfor this reason prohibited to vary the threshold between the maximum andminimum densities P_(Cmax) and P_(Cmin) of the peak zones P_(B) andP_(C), respectively, in binarizing the pixel densities of a frame ofimage on a character document.

FIG. 8 shows the distribution of the pixel densities of a frame of imagewhich may be picked up from, for example, a photographic document, thedensities being also expressed in hexadecimal notation. As will be seenfrom the curve indicated in FIG. 8, the pixel densities of a frame ofimage on a photographic document occur with practically equalfrequencies practically throughout the range of densities between thelower and upper limit densities corresponding to pure white (00(H)) andpure black (FF(H)), respectively.

The densities of the pixels forming a frame image on this type ofdocument can also be binarized advantageously in the simple binarizationmode of image reading operation. In the case of a photographic document,however, the threshold value for use in the simple binarization mode ofimage reading operation, that is, the representative value of the ditherpattern is preferably selected to intervene between predeterminedmaximum and minimum densities Q_(max) and Q_(min) close to the upper andlower limit densities corresponding to pure white and pure black,respectively. The use of such a threshold value will prove advantageousfor precluding the fading and blackening of image elements. It may alsobe noted that, for the binarization of the pixel densities of a frame ofimage on a photographic document, it is useful to minutely vary thethreshold because of the fact that there are a number of pixel densitiesdistributed between the maximum and minimum values densities Q_(max) andQ_(min) of the original pixel densities.

In the first preferred embodiment of an image reading apparatusaccording to the present invention, the original pixel densities of aframe of image are thus binarized by following a manipulative procedurewhich is started by depression of either the character mode select key158 or the halftone mode select key 160 on the control panel 140A. Thedensity "plus" key 164 or the density "minus" key 166 is then depressedto enter an instruction to increase or decrease the valid degree oflightness for image reading.

Each time the density "plus" key 164 is depressed, the valid density forimage reading is stepwise increased a predetermined value and highlightis moved from any of the subsections of the density indicator section162 to the subsection located to the right of the former. When thesimple binarization mode of image reading operation is selected with thecharacter mode select key 158 depressed, only the valid degree oflightness indicated by letter "D", "M" or "L" or numeral "4", "5" or "6"can be selected. If the density "plus" key 164 is depressed after theindicator subsection corresponding to the degree of lightness indicatedby letter "L" or numeral "6" is highlighted, the subsectioncorresponding to the higher degree of lightness indicated by numeral "7"will not be highlighted.

Similarly, the valid density for image reading is stepwise decreased apredetermined value each time the density "minus" key 166 is depressed,and highlight is moved from any of the subsections of the densityindicator section 162 to the subsection located to the left of theformer. When the simple binarization mode of image reading operation isselected with the character mode select key 158 depressed and thedensity "minus" key 166 is depressed after the indicator subsectioncorresponding to the degree of lightness indicated by letter "D" ornumeral "4" is highlighted, the subsection corresponding to the lowerdegree of lightness indicated by numeral "3" will not be highlighted.

FIG. 9 shows a control circuit 170A for use in the first preferredembodiment of an image reading apparatus according to the presentinvention.

The control circuit 170A comprises a semiconductor central processingunit 172 responsive to command signals produced from the control panel140A and signals produced by various sensors and detectors provided inthe apparatus embodying the present invention. The command signals to besupplied from the control panel 140A include signals, commonly denotedby S_(CMD), generated from the scan start key 142, common clear key 144,image scale-up and scale-down keys 148 and 150, and sheet size selectkeys 154 and 156. The command signals from the control panel 140Afurther include a character mode select signal S_(CM) to be suppliedfrom the character mode select key 158, a halftone mode select signalS_(HM) to be supplied from the halftone mode select key 160, a densitystep-up signal S_(D+) to be supplied from the density "plus" key 164,and a density step-down signal S_(D-) to be supplied from the density"minus" key 166.

The signals supplied from the sensors and detectors provided in theapparatus include signals, commonly denoted by S_(MV), indicating thedetected speeds of rotation of the scanner drive motor 132 (M1),lens/sensor drive motor 134 (M2) and sensor drive motor 136 (M3),respectively. The signals from the sensors and detectors further includesignals, commonly denoted by S_(POS), indicating the detected currentpositions of the lamp/mirror carrier 118, mirror carrier 120,lens/sensor carrier 126, and sensor holder 130. The signal S_(POS) thussupplied from the detecting means provided in association with each ofthe lamp/mirror carrier 118 and mirror carrier 120 is used to check ifthe associated carrier 118 or 120 is in a predetermined home positionwith respect to the document support table 102.

The central processing unit 172 further receives signals from variousassociated hardware units which include a clock generator circuit 174which outputs clock pulses S_(CK) and a line memory 176 implemented by asemiconductor random-access memory (RAM). The data to be stored in theline memory 176 include data representative of the detected focusadjusting pattern, reduction/magnification ratio detecting pattern, andshading data correcting pattern printed on the lower face of thedocument scale 104 arranged on the upper panel of the housing structure100.

Responsive to these signals, the central processing unit 172 outputsvarious control signals to control the operation of various mechanicaland optical functional units of the apparatus. The control signals thusoutput from the central processing unit 172 include motor actuationsignals S_(MD1), S_(MD2) and S_(MD3) to be supplied to driver circuits178, 180 and 182 for actuating the scanner drive motor 132, lens/sensordrive motor 134 and sensor drive motor 136, respectively. The signals tobe output from the central processing unit 172 further include a controlsignal S_(EXP) to be supplied to a voltage regulator circuit 184 for theexposure lamp 106 and signals, commonly denoted by S_(IND), to besupplied to the indicators on the control panel 140A such as thenumerical display section 146, sheet size indicator section 152, anddensity indicator section 162 provided on the control panel 140A.Responsive to the signal S_(EXP) supplied from the central processingunit 172, the voltage regulator circuit 184 outputs a lamp controlvoltage signal V_(EXP) with which the exposure lamp 106 is to beactivated to illuminate.

The central processing unit 172 further supplies signals to variousassociated hardware units which include an analog-to-digital (A/D)converter 186 which has an input terminal connected to the CCD imagesensor 128. The image sensor 128 is responsive to sample-and-holdsignals S_(SH) supplied from the clock generator circuit 174 and outputsanalog image density data signals S_(DV) representative of the imageinformation contained in a beam of light incident on the sensor 128. Theanalog-to-digital converter 186 receives these analog image density datasignals from the array of the charge-coupled devices forming the imagesensor 128 and outputs corresponding digital signals S_(DD) on the basisof reference voltage signals S_(REF) supplied from the centralprocessing unit 172. The digital signals S_(DD) thus output from theanalog-to-digital converter 186 are supplied to a shading circuit 188which compensates for the spurious components in the supplied signalsS_(DD) to eliminate the irregularities in the quantities of lightincident on the individual charge-coupled devices forming the imagesensor 128 and the irregularities in the degrees of sensitiveness of thecharge-coupled devices. The shaded digital image density data signalsS_(SDD) thus output from the shading generator circuit 188 arerepresentative of the original pixel densities of the frame of imagedetected from the document D currently in use. The image density data inthe form of the shaded digital image density data signals S_(SDD) is onone hand stored in the line memory 176 and on the other hand supplied toa binarizing comparator circuit 190.

The data required for the shading process to be carried out in theshading circuit 188 is supplied from the central processing unit 172.For this purpose, the central processing unit 172 reads the shading datacorrecting pattern detected from the lower face of the document scale104 and stored in the line memory 176. On the basis of the shading datacorrecting pattern thus read from the line memory 176, the centralprocessing unit 172 formulates the data in accordance with which shadingsignals are generated in the shading circuit 188.

The signals output from the central processing unit 172 further includea write/read control signal S_(R/W) to be supplied to the line memory176, a simple binarization image-density signal S_(BD) to be supplied toa simple binarization threshold generator circuit 192, and a halftoneimage-density signal S_(HD) to be supplied to a halftone thresholdgenerator circuit 194. The simple binarization threshold generatorcircuit 192 is responsive to the simple binarization image-densitysignal S_(BD) to output a simple binarization threshold signal S_(BT)indicative of a fixed threshold value for use in the simple binarizationmode of image reading operation, while the halftone threshold generatorcircuit 194 is responsive to the halftone image-density signal S_(HD) tooutput a halftone threshold signal S_(HT) indicative of a stepwisevariable threshold value for use in the halftone mode of image readingoperation. The simple binarization threshold signal S_(BT) thus outputfrom the simple binarization threshold generator circuit 192 or thehalftone threshold signal S_(HT) output from the halftone thresholdsignal generator circuit 194 is supplied to the binarizing comparatorcircuit 190 through a simple-binarization/halftone mode selector circuit196. The simple-binarization/halftone mode selector circuit 196 becomesselectively transparent to the simple binarization threshold signalS_(BT) or the halftone image-density signal S_(HD) depending on a modeselect signal S_(MODE) supplied from the central processing unit 172 tothe control terminal of the selector circuit 196.

The image density data in the form of the shaded digital image densitydata signals S_(SDD) supplied to the binarizing comparator circuit 190is compared with the simple binarization threshold signal S_(BT)supplied from the simple binarization threshold generator circuit 192 orthe halftone image-density signal S_(HD) supplied from the halftonethreshold signal generator circuit 194 through thesimple-binarization/halftone mode selector circuit 196. The binarizingcomparator circuit 190 is thus operative to output binary image signalsS_(OUT) each of logic "1" or "0" state responsive to the shaded digitalimage density data signals S_(SDD) and supplies the output signalsS_(OUT) to an image signal output circuit 198. The image signal outputcircuit 198 receives, in addition to the binary image signals S_(OUT)from the comparator 190, a valid image area signal S_(VIA) of logic "1"or "0" state supplied from the central processing unit 172.

Responsive to the binary image signals S_(OUT) supplied from thebinarizing comparator circuit 190, the image signal output circuit 198combines each of the binary image signals S_(OUT) with the valid imagearea signal S_(VIA) of logic "1" or "0" state from the centralprocessing unit 172 in a logic "AND" operation. The resultant binarysignals are delivered to a signal processing circuit of any externaloutput unit such as a printer or a display unit (not shown) to reproducethe image represented by the output signals from the signal outputcircuit 198.

If desired, the simple-binarization/halftone mode selector circuit 196may be dispensed with so that the simple binarization threshold signalS_(BT) or the halftone image-density signal S_(HD) is selectively passedto the binarizing comparator 190 depending on the selected mode of imagereading.

FIG. 10 shows a main routine program to be executed by the centralprocessing unit 172 included in the control circuit 170A hereinbeforedescribed with reference to FIG. 9.

The execution of the main routine program shown in FIG. 10 is startedwhen the apparatus is initially switched in. The main routine programstarts with step A01 at which the registers included in the centralprocessing unit 172 and the line memory 176 are reset. The step A01 isfollowed by step A02 to check for any command signal supplied from thecontrol panel 140A. The command signal to be checked for at this stepA02 may be the signal S_(CMD) supplied from any of the scan start key142, common clear key 144, image scale-up and scale-down keys 148 and150 and sheet size select keys 154 and 156, or the character mode selectsignal S_(CM) supplied from the character mode select key 158, thehalftone mode select signal S_(HM) supplied from the halftone modeselect key 160, the density step-up signal S_(D+) supplied from thedensity "plus" key 164, or the density step-down signal S_(D-) suppliedfrom the density "minus" key 166. In the absence detected of any commandsignal S_(CMD) supplied from the control panel 140A, the centralprocessing unit 172 repeats the step A02 until it is found that there isany command signal S_(CMD) received from the control panel 140A.

The central processing unit 172 proceeds to step A03 and executes a modeshift subroutine program if it is detected at step A02 that there is thesignal from the image scale-up or scale-down key 148 or 150, the signalfrom the sheet size select key 154 or 156, the character mode selectsignal S_(CM) from the character mode select key 158, the halftone modeselect signal S_(HM) from the halftone mode select key 160, the densitystep-up or step-down signal S_(D+) or S_(D-) from the density "plus" or"minus" key 164 or 166. Responsive to any of these signals supplied fromthe control panel 140A, the central processing unit 172 executes thesteps required by the supplied signal on condition that the mode ofoperation requested by the signal is validly acceptable in theapparatus. The details of this mode shift subroutine program A03 will behereinafter described with reference to FIG. 11.

On the other hand, if it is detected at step A02 that there is thesignal supplied from the scan start key 142 on the control panel 140A,the central processing unit 172 proceeds to subroutine program A04 andexecutes an image read control subroutine program. The details of thisimage read control subroutine program A04 will be hereinafter describedwith reference to FIGS. 12A and 12B.

Referring to FIG. 11, the mode shift subroutine program A03 included inthe routine program described with reference to FIG. 10 starts with stepB01 to determine which command signal is received from the control panel140A. Thus, if it is detected at step B01 that there is the signalreceived from the sheet size select key 154 or 156, the centralprocessing unit 172 proceeds to step B02 to check if the request for thesize of print output sheets designated by the signal received is validlyacceptable in the apparatus and/or the external printer unit. If theanswer for this step B02 is given in the affirmative, the centralprocessing unit 172 proceeds to step B03 to select the size of printoutput sheets designated by the signal received and thereafter revertsto the main routine program described with reference to FIG. 10 to checkif any other command signal is received from the control panel 140A. Ifit is determined at step B02 that the request for the size of printoutput sheets designated by the signal received is not validlyacceptable and accordingly the answer for step B02 is given in thenegative, the central processing unit 172 immediately reverts to themain routine program described with reference to FIG. 10 to check if anyother command signal is received from the control panel 140A.

If it is detected at step B01 that there is the signal received from theimage scale-up or scale-down key 148 or 150, the central processing unit172 proceeds to step B04 to check if the request for thereduction/magnification ratio designated by the signal received isvalidly acceptable in the apparatus and/or the external printer unit. Ifthe answer for this step B04 is given in the affirmative, the centralprocessing unit 172 proceeds to step B05 to select thereduction/magnification ratio designated by the signal received andthereafter reverts to the main routine program described with referenceto FIG. 10 to check if any other command signal is received from thecontrol panel 140A. If it is determined at step B04 that the request forthe reduction/magnification ratio designated by the signal received isnot validly acceptable and accordingly the answer for step B04 is givenin the negative, the central processing unit 172 immediately reverts tothe main routine program described with reference to FIG. 10 to check ifany other command signal is received from the control panel 140A.

If it is detected at step B01 that there is the character mode selectsignal S_(CM) received from the character mode select key 158 or thehalftone mode select signal S_(HM) from the halftone mode select key160, the central processing unit 172 proceeds to step B06 to check ifthe request for the simple binarization or halftone mode of imagereading operation requested by the signal S_(CM) or S_(HM) received isvalidly acceptable in the apparatus. If the answer for this step B06 isgiven in the affirmative, the central processing unit 172 proceeds tostep B07 to select the simple binarization or halftone mode of imagereading operation requested by the signal S_(CM) or S_(HM) received andthereafter reverts to the main routine program described with referenceto FIG. 10 to check if any other command signal is received from thecontrol panel 140A. If it is determined at step B06 that the request forthe mode of image reading operation requested by the signal received isnot validly acceptable and accordingly the answer for step B06 is givenin the negative, the central processing unit 172 immediately reverts tothe main routine program described with reference to FIG. 10 to check ifany other command signal is received from the control panel 140A.

If it is detected at step B01 that there is the density step-up orstep-down signal S_(D+) or S_(D-) received from the density "plus" key164 or density "minus" key 166, the central processing unit 172 proceedsto step B08 to check if there is the character mode select signal S_(CM)received from the character mode select key 158. If the answer for thisstep B08 is given in the affirmative, the central processing unit 172proceeds to step B09 to check if the request for the density for imagereading designated by the signal S_(D+) or S_(D-) received is validlyacceptable in the simple binarization mode of image reading operation.If the answer for this step B09 is given in the affirmative, the centralprocessing unit 172 proceeds to step B10 to select the density for imagereading designated by the signal S_(D+) or S_(D-) received for theselected simple binarization mode of image reading operation andthereafter reverts to the main routine program described with referenceto FIG. 10 to check if any other command signal is received from thecontrol panel 140A.

If it is determined at step B08 that there is not the character modeselect signal S_(CM) received from the character mode select key 158 andas such the answer for step B08 is given in the negative, the centralprocessing unit 172 proceeds to step B11 to check if the request for thedensity for image reading designated by the signal S_(D+) or S_(D-)received is validly acceptable in the halftone mode of image readingoperation. If the answer for this step B11 is given in the affirmative,the central processing unit 172 proceeds to step B12 to select thedensity for image reading designated by the signal S_(D+) or S_(D-)received for the selected halftone mode of image reading operation andthereafter reverts to the main routine program described with referenceto FIG. 10 to check if any other command signal is received from thecontrol panel 140A. If it is determined at step B11 that the request forthe density for image reading designated by the signal S_(D+) or S_(D-)received is not validly acceptable and accordingly the answer for stepB11 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 10 to check if any other command signal is received from thecontrol panel 140A.

On the other hand, when it is detected at step A02 in the main routineprogram that there is present the signal supplied from the scan startkey 142 on the control panel 140A, the central processing unit 172executes the image read control subroutine program A04.

As shown in FIG. 12A, the image read control subroutine program A04starts with step C01 at which the central processing unit 172 suppliesthe control signal S_(EXP) to the voltage regulator circuit 184 for theexposure lamp 106. Responsive to the signal S_(EXP) thus received fromthe central processing unit 172, the voltage regulator circuit 184outputs the lamp control voltage signal V_(EXP) to activate the exposurelamp 106 to illuminate. The central processing unit 172 then proceeds tostep C02 to check if each of the lamp/mirror carrier 118 and mirrorcarrier 120 is held in a predetermined home position with respect to thedocument support table 102. This decision is made on the signal S_(POS)supplied from the detecting means provided in association with each ofthe lamp/mirror carrier 118 and mirror carrier 120.

If it is found at this step C02 that the lamp/mirror carrier 118 andmirror carrier 120 are not held in their respective home positions, thecentral processing unit 172 proceeds to step C03 to supply the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step C04 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The loop of the steps C03 and C04 is repeateduntil it is confirmed at step C04 that the lamp/mirror and mirrorcarriers 118 and 120 have reached their respective home positions. Whenit is thus found at step C04 that the carriers 118 and 120 have reachedtheir respective home positions and accordingly the answer for the stepC04 turns affirmative, the central processing unit 172 proceeds to stepC05 to reset the signal S_(MD1) and stop the scanner drive motor 132.

Subsequently to this step C05 or when it is confirmed at step C04 thatthe lamp/mirror and mirror carriers 118 and 120 are held in theirrespective home positions, the central processing unit 172 proceeds tostep C06 to supply the motor actuation signal S_(MD1) for a second timeto the motor driver circuit 178 for the scanner drive motor 132.Responsive to the motor actuation signal S_(MD1) thus received from thecentral processing unit 172, the motor driver circuit 178 actuates thescanner drive motor 132 into operation to move the lamp/mirror andmirror carriers 118 and 120 forwardly from their home positions in thedirections indicated by arrowheads a and b in FIG. 1. The document Dplaced on the document support table 102 is now optically scanned by theexposure lamp 106 and the resultant image-bearing beam of light B isdirected past the reflector mirrors 110, 112 and 114 to the image sensor122.

The step C06 is followed by step C07 at which the central processingunit 172 reads the shading data correcting pattern detected from thelower face of the document scale 104 and stored in the line memory 176.On the basis of the shading data correcting pattern read from the linememory 176, the central processing unit 172 formulates the data inaccordance with which shading signals are to be generated in the shadingcircuit 188. The data thus generated in the central processing unit 172is stored into the line memory 176.

The central processing unit 172 then detects at step C08 whether or notthe lamp/mirror carrier 118 and mirror carrier 120 have reached thepositions effective to scan the leading end of the document D placed onthe document support table 102. The step C08 is repeated until it isconfirmed that the document D on the document support table 102 isscanned at its leading end. When it is thus determined at step C08 thatthe document D on the document support table 102 is scanned at itsleading end and accordingly the answer for the step C08 turnsaffirmative, the central processing unit 172 proceeds to step C09 (FIG.12B) to generate the valid image area signal S_(VIA). The valid imagearea signal S_(VIA) thus generated by the central processing unit 172 atstep C09 is supplied to the control terminal of the image signal outputcircuit 198.

Subsequently to step C09, the central processing unit 172 detects atstep C10 whether or not the lamp/mirror carrier 118 and mirror carrier120 have reached the positions effective to scan the trailing end of thedocument D on the document support table 102. The step C10 is repeateduntil it is confirmed that the document D on the document support table102 has been scanned to its trailing end. When it is thus determined atstep C10 that the scanning of the document D on the document supporttable 102 is complete and accordingly the answer for the step C10 turnsaffirmative, the central processing unit 172 proceeds to step C11 toreset the valid image area signal S_(VIA) which has been supplied to thecontrol terminal of the image signal output circuit 198.

The central processing unit 172 then proceeds to step C12 to cease thesupply of the control signal S_(EXP) to the voltage regulator circuit184 to de-activate the exposure lamp 106. The step C12 is followed bystep C13 at which the central processing unit 172 supplies the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step C14 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The steps C14 is repeated until it isconfirmed that the lamp/mirror and mirror carriers 118 and 120 havereached their respective home positions. When it is thus found at stepC14 that the carriers 118 and 120 have reached their respective homepositions and accordingly the answer for the step C14 turns affirmative,the central processing unit 172 proceeds to step C15 to reset the signalS_(MD1) and stop the scanner drive motor 132. Subsequently, the centralprocessing unit 172 reverts to the main routine program described withreference to FIG. 10 to check if any other command signal is receivedfrom the control panel 140A.

Second Preferred Embodiment (FIG. 13 to FIGS. 19A and 19B)

Description will be hereinafter made in regard to a second preferredembodiment of an image reading apparatus according to the presentinvention. The second preferred embodiment of the present invention ischaracterized by the capabilities to designate a particular local areawithin a document and read the image in the particular area in a desiredmode of image reading operation. In the second preferred embodiment ofthe present invention is also used the mechanical and opticalarrangement described with reference to FIG. 1.

FIG. 13 shows an editor module 200A which forms part of the secondpreferred embodiment of the present invention. The editor module 200Alargely consists of a tablet section 202 and a key section 204comprising a total of nine control keys. The tablet section 202 of theeditor module 200A is used to define a desired local area within theimage-carrying document to be reproduced. For this purpose, the documentD to be reproduced is placed on the tablet section 202 as shown andthereupon a light pen is used to specify particular coordinate points todefine the desired local area of the document D. To define asquare-shaped rectangular area of the document D, only the locations ofthe opposite ends of one diagonal of the area may be specified with useof a light pen.

The control keys provided in the key section 204 of the editor module200A include:

a trimming key "F1" used to enter an instruction to blank out (or "whiteout") the image outside the specified local area of the document D onthe tablet section 202,

a masking key "F2" used to enter an instruction to blank out the imagewithin the specified local area of document on the tablet section 202,

a white/black reverse key "F3" used to enter an instruction for thereversal of the white and black features of an image on the document,

a simple binarization mode select "F4" used to enter an instruction toselect the simple binarization mode of image reading operation for thedocument on the tablet section 202 and use a fixed threshold value forthe simple binarization mode of image reading operation,

a first dither-pattern halftone mode select key "F5" used to enter aninstruction to select the halftone mode of image reading operation forthe document on the tablet section 202 and use a first prescribed ditherpattern for determining the threshold value in the halftone mode ofimage reading operation,

a second dither-pattern halftone mode select key "F6" used to enter aninstruction to select the halftone mode of image reading operation forthe document on the tablet section 202 and use a second prescribeddither pattern for determining the threshold value in the halftone modeof image reading operation,

a trim/mask cancel key "F7" used to enter an instruction to cancel theinstruction which has been entered to blank out the image outside orinside the specified local area of the document on the tablet section202,

a data-clear key "C" used to enter an instruction to clear all the datawhich have been entered to define a local area within the document onthe table section 202, and

a data-send key "S" used to enter an instruction to transmit to thecontrol circuit of the apparatus the data and instructions enteredthrough the editor module 200A in respect of the document on the tablesection 202.

Thus, the second preferred embodiment of the present invention hasseveral kinds of attributes of image reading operation. These attributesof image reading operation include

whiting (or blackening) out the image outside or inside a specifiedlocal area of a document in accordance with a command signal suppliedfrom the key "F1" or "F2",

reversing the white and black features of an image on a document inaccordance with a command signal supplied from the key "F3",

selecting the simple binarization or halftone mode of image readingoperation in accordance with a command signal supplied from the key "F4"or one of the keys "F5" and "F6", and

selecting the first or second prescribed dither pattern for the halftonemode of image reading operation in accordance with a command signalsupplied from the key "F5" or "F6".

It may be noted that, when the trimming key "F1" or the masking key "F2"is depressed with the white/black reverse key "F3" depressed, the imageoutside or inside the specified local area of the document is blackenedout.

FIG. 14 shows an example of the key/indicator configuration of a controlpanel 140B which also forms part of the second preferred embodiment ofan image reading apparatus according to the present invention. On thecontrol panel 140B are provided a scan start key 142, a common clear key144, a four-digit eight-segment numerical display section 146, an imagescale-up key 148, an image scale-down key 150, a sheet size indicatorsection 152, a first sheet size select key 154, a second sheet sizeselect key 156, a character mode select key 158, and a halftone modeselect key 160. The functions of these keys and display/indicatorsections on the control panel 140B are similar to those of theirrespective equivalents in the control panel 140A described withreference to FIG. 2 and will not be herein described with reference toFIG. 14.

On the control panel 140B of the second preferred embodiment of thepresent invention are further provided first and second densityindicator sections 162a and 162b each consisting of a series ofsubsections arranged in the of lightness indicated by numerals "1" to"9". The first density indicator section 162a is used to indicate theselected density for image reading in the simple binarization mode ofimage reading operation selected by the character mode select key 158,while the second density indicator section 162b is used to indicate theselected density for image reading in the halftone mode of image readingoperation selected by the halftone mode select key 160. The selecteddensity for image reading is shown highlighted such as the density "4"in the simple binarization mode density indicator section 162a and thedensity "5" in the halftone mode density indicator section 162b.

In association with the simple binarization mode density indicatorsection 162a are provided a character density "plus" key 164a used toenter an instruction to increase the valid degree of lightness for imagereading in the simple binarization mode and a character density "minus"key 166a used to enter an instruction to decrease the valid degree oflightness for image reading in the simple binarization mode of imagereading operation. Similarly, the halftone mode density indicatorsection 162a has provided in association therewith a halftone density"plus" key 164b used to enter an instruction to increase the validdegree of lightness for image reading in the halftone mode and ahalftone density "minus" key 166b used to enter an instruction todecrease the valid degree of lightness for image reading in the halftonemode of image reading operation.

The control panel 140B shown in FIG. 14 further comprises an editorcommunication grant key 206 (labelled "ED") used to enter an instructionto grant reception of data and commands from the editor module 200A, andan editor information display section 208 for visually indicating thedata received from the editor module 200A. When the editor communicationgrant key 206 is depressed after the key 206 was once depressed, theinstruction which has been entered to grant reception of data andcommands from the editor module 200A is cancelled and entry of data andcommand signals through the editor module 200A is invalidated.

It is now assumed that there is an operator who desires to produce aprint out of a document D or otherwise reproduce the image on thedocument D. The operator of the apparatus will first depress the editorcommunication grant key 206 to enable the control panel 140B to grantreception of the data and commands to be generated in the editor module200A. The operator may then specify particular coordinate points todefine a desired local area of the document D through manipulation of alight pen with the document D placed on the tablet section 202. Theoperator may thereafter depress any of the keys "F1" to "F6" on theeditor module 200A to select any of the attributes of the image readingoperation to be performed.

Thus, the operator of the apparatus may depress the key "F1" or "F2" toblank out the image outside or inside the specified local area of thedocument D, the key "F3" to reverse the white and black features of animage on a document with use of the key "F3", or the key "F4", "F5" or"F6" to select the simple binarization or halftone mode of image readingoperation.

The valid density for image reading in the second preferred embodimentof the present invention is designated with use of any of the density"plus" and "minus" keys 164a, 166a, 164b and 166b provided on thecontrol panel 140B. When the valid density for image reading is thusdesignated from the character density "plus" or "minus" key 164a or 166aor the halftone density "plus" or "minus" key 164b or 166b on thecontrol panel 140B, it is detected that the density required is validlyacceptable in the apparatus and/or the external printer unit associatedwith the apparatus. This detection is made by a central processing unitincorporated in the control circuit to be described. If it is determinedthat the density required from the key 164a, 166a, 164b or 166b isvalidly acceptable, the data representing the density is stored into amemory incorporated in the central processing unit. In this instance, ifthe valid density for image reading is designated from the characterdensity "plus" or "minus" key 164a or 166a with the simple binarizationmode of image reading operation selected from the character mode selectkey 158 on the control panel 140B, the data representing the density isstored into the simple binarization mode density storage area of theinternal memory of the central processing unit. Likewise; when the validdensity for image reading is designated from the halftone density "plus"or "minus" key 164b or 166b with the halftone mode of image readingoperation selected from the halftone mode select key 160 on the controlpanel 140B, the data representing the density is stored into thehalftone mode density storage area of the internal memory of the centralprocessing unit.

The operator who has selected any of the attributes allocated to thekeys "F1" to "F6" on the editor module 200A may thus desire to changethe valid density for image reading through manipulation of any of thedensity "plus" and "minus" keys 164a, 166a, 164b and 166b on the controlpanel 140B. When any of the density "plus" and "minus" keys 164a, 166a,164b and 166b on the control panel 140B is depressed, the valid densityfor image reading is stepwise increased or decreased a predeterminedvalue and highlight is moved from any of the subsections of the firstdensity indicator section 162a or the second density indicator section162a to the subsection adjacent the former.

The operator of the apparatus may then depress the data-send key "S" toenter an instruction to transmit to the control circuit of the apparatusthe data and instructions which have been entered through the editormodule 200A.

FIG. 15 shows the general construction and arrangement of a controlcircuit 170B for use in the second preferred embodiment of an imagereading apparatus according to the present invention. The controlcircuit 170B for use in the second preferred embodiment of the presentinvention is essentially similar to the control circuit 170Ahereinbefore described with reference to FIG. 9 but, in the controlcircuit herein shown, the central processing unit 172 is responsive notonly to the various command signals supplied from the control panel 140Bbut to various data and command signals S_(ED) generated in and suppliedfrom the editor module 200A. These data and command signals S_(ED)supplied from the editor module 200A are allowed into the centralprocessing unit 172 of the control circuit 170B in the presence of asignal generated with the editor communication grant key 206 depressedto enter an instruction to grant reception of data and commands from theeditor module 200A.

In the control circuit 170B illustrated in FIG. 15, the centralprocessing unit 172 may further receive a density step-up signal S_(D1+)from the character density "plus" key 164a, a density step-down signalS_(D1-) from the character density "minus" key 166a, a density step-upsignal S_(D2+) from the halftone density "plus" key 164b, a densitystep-down signal S_(D2-) from the halftone density "minus" key 166b. Ashas been noted, the central processing unit 172 provided in the controlcircuit 170B of the second preferred embodiment of the present inventionhas incorporated therein an internal memory 210 having a simplebinarization mode density storage area 210a and a halftone mode densitystorage area 210b, as shown. Thus, when the valid density for imagereading is designated from the density "plus" or "minus" key 164a or166a with the simple binarization mode of image reading operationselected from the character mode select key 158 on the control panel140B, the data representing the density is stored into the simplebinarization mode density storage area 210a of the internal memory 210On the other hand, when the valid density for image reading isdesignated from the halftone density "plus" or "minus" key 164b or 166bwith the halftone mode of image reading operation selected from thehalftone mode select key 160 on the control panel 140B, the datarepresenting the density is stored into the halftone mode densitystorage area 210b of the internal memory.

Responsive to the data and command signals S_(ED) supplied from theeditor module 200A and/or to the signal supplied from any of the density"plus" and "minus" keys 164a, 164b, 166a and 166b on the control panel140B, the central processing unit 172 generates a four-bit attributesignal S_(ATT) indicative of selected ones of the attributes of imagereading operation. The attribute signal S_(ATT) thus representative ofthe selected attributes of image reading operation is supplied to andstored into an attribute memory 212 implemented by a semiconductorrandom-access memory. Fractions of the signal S_(ATT) thus stored intothe attribute memory 212 are supplied to the binarizing comparatorcircuit 190, halftone threshold generator circuit 194,simple-binarization/halftone mode selector circuit 196, and image signaloutput circuit 198 as will be described in more detail.

In the control circuit 170B illustrated in FIG. 15, furthermore, theimage signal output circuit 198 has two input terminals one of which isconnected directly to the output terminal of the binarizing comparatorcircuit 190 and the other of which is connected through an inverter 214to the output terminal of the comparator circuit 190. The binary imagesignals S_(OUT) produced by the binarizing comparator circuit 190responsive to the shaded digital image density data signals S_(SDD) fromthe shading circuit 188 are thus supplied in true or non-inverted formto one input terminal of the output circuit 198 and in inverted form tothe other input terminal of the output circuit 198.

The signal S_(ATT) to be generated by the central processing unit 172and stored into the attribute memory 212 is indicative of four differentkinds of attributes in respect of an image pixel having a unit areameasuring 1 mm by 1 mm and is provided in the form of a sequence of fourbits d₃, d₂, d₁ and d₀ each of logic "1" or "0" state.

The bit d₃ of the attribute signal S_(ATT) provides a first fraction ofthe signal S_(ATT) and indicates selection of the blanking out of animage pixel when set to logic "0" state and selection of thenon-blanking of a pixel when set to logic "1" state. The bit d₃ of theattribute signal S_(ATT) is set to logic "0" state when the trimming key"F1" or the masking key "F2" on the editor module 200A is depressed. Thefirst fraction of the attribute signal S_(ATT) thus provided by the bitd₃ of the signal S_(ATT) is supplied to one control terminal of thebinarizing comparator circuit 190 and, when the bit d₃ is set to logic"0" state, enables the comparator circuit 190 to white out the specifiedimage pixel (or blacken out the pixel in the presence of the white/blackreversing bit d₂ of logic "1" state) as will be described in moredetail. To the other control terminal of the binarizing comparatorcircuit 190 is supplied either the simple binarization threshold signalS_(BT) output from the simple binarization threshold generator circuit192 or the halftone threshold signal S_(HD) output from the halftonethreshold generator circuit 194 depending on the logic state of the bitd₁ applied to the selector circuit 196.

The bit d₂ of the attribute signal S_(ATT) provides a second fraction ofthe signal S_(ATT) and indicates selection of the non-reversing of thewhite and black features of an image when set to logic "0" state andselection of the reversing of the white and black features of an imagewhen set to logic "1" state. The bit d₂ of the attribute signal S_(ATT)is set to logic "1" state when the white/black reverse key "F3" on theeditor module 200A is depressed. The second fraction of the attributesignal S_(ATT) thus provided by the bit d₂ of the signal S_(ATT) issupplied to one control terminal of the image signal output circuit 198.To another control terminal of the image signal output circuit 198 issupplied a valid image area signal S_(VIA) of logic "1" or "0" statefrom the central processing unit 172 as in the control circuit 170A(FIG. 9) used in the first preferred embodiment of the presentinvention. Thus, the image signal output circuit 198 in the controlcircuit 170B of the second preferred embodiment of the present inventionreceives the binary image signals S_(OUT) supplied both in inverted andnon-inverted forms from the binarizing comparator circuit 190, the bitd₂ of the attribute signal S_(ATT) supplied from the attribute memory212, and the valid image area signal S_(VIA) supplied from the centralprocessing unit 172.

The bit d₁ of the attribute signal S_(ATT) provides a third fraction ofthe signal S_(ATT) and indicates selection of the simple binarizationmode of image reading operation when set to logic "0" state andselection of the halftone mode of image reading operation when set tologic "1" state. The bit d₁ of the attribute signal S_(ATT) is set tologic "0" state when the simple binarization mode select key "F4" on theeditor module 200A is depressed. The third fraction of the attributesignal S_(ATT) thus provided by the bit d₁ of the signal S_(ATT) issupplied to the control terminal of the simple-binarization/halftonemode selector circuit 196. Responsive to this mode select bit d₁, thesimple-binarization/halftone mode selector circuit 196 supplies eitherthe simple binarization threshold signal S_(BT) or the halftonethreshold signal S_(HD) depending on the logic state of the bit d₁.

The bit d₀ of the attribute signal S_(ATT) provides a fourth fraction ofthe signal S_(ATT) and indicates selection of the first prescribeddither pattern simple binarization when set to logic "0" state andselection of the the second dither pattern when set to logic "1" state.The bit d₀ of the attribute signal S_(ATT) is set to logic "0" statewhen the first dither-pattern halftone mode select key "F5" on theeditor module 200A is depressed and is set to logic "1" state when thesecond dither-pattern halftone mode select key "F6" on the editor module200A is depressed. The fourth fraction of the attribute signal S_(ATT)thus provided by the bit d₀ of the signal S_(ATT) is supplied to thehalftone threshold generator circuit 194, which is thus enabled toselect the first or second prescribed dither pattern depending on thelogic state of the bit d₀.

As will be seen from the above discussion, the four-bit attribute signalS_(ATT) is effective to designate any combination of the four differentattributes each having two possibilities in respect of each image pixelmeasuring 1 mm by 1 mm. Among the possible combinations of suchattributes are:

    ______________________________________                                        d.sub.3                                                                            d.sub.2                                                                              d.sub.1                                                                              d.sub.0                                                    ______________________________________                                        0    0      x      x    . . . select whiting out                              0    1      x      x    . . . select blackening out                           1    0      0      x    . . . select simple binarization                                                    threshold                                       1    0      1      0    . . . select first dither pattern                     1    0      1      1    . . . select second dither pattern                    1    1      0      x    . . . select white/black reversing                                                  and simple binarization                                                       threshold                                       1    1      1      0    . . . select white/black reversing                                                  and first dither pattern                        1    1      1      1    . . . select white/black reversing                                                  and second dither pattern                       ______________________________________                                    

As has been described in regard to the control circuit 170A of the firstpreferred embodiment of the present invention, the image density data inthe form of the shaded digital image density data signals S_(SDD)supplied to the binarizing comparator circuit 190 is compared with thesimple binarization threshold signal S_(BT) supplied from the simplebinarization threshold generator circuit 192 or with the halftoneimage-density signal S_(HD) supplied from the halftone threshold signalgenerator circuit 194 through the simple-binarization/halftone modeselector circuit 196. The binarizing comparator circuit 190 is thusoperative to generate binary image signals each of logic "1" or "0"state responsive to the shaded digital image density data signalsS_(SDD).

In the meantime, the data representing the valid density for imagereading stored in the simple binarization mode density storage area 210aor the halftone mode density storage area 210b of the internal memory210 is loaded into the simple binarization threshold generator circuit192 as the simple binarization image-density signal S_(BD) or into thehalftone threshold generator circuit 194 as the halftone image-densitysignal S_(HD). Responsive to the simple binarization image-densitysignal S_(BD) or the halftone image-density signal S_(HD) thus suppliedfrom the central processing unit 172, the simple binarization thresholdgenerator circuit 192 outputs the simple binarization threshold signalS_(BT) indicative of a fixed threshold value for use in the simplebinarization mode of image reading operation, or the halftone thresholdgenerator circuit 194 outputs a halftone threshold signal S_(HT)indicative of a stepwise variable threshold value for use in thehalftone mode of image reading operation. The simple binarizationthreshold signal S_(BT) thus output from the simple binarizationthreshold generator circuit 192 or the halftone threshold signal S_(HT)output from the halftone threshold signal generator circuit 194 issupplied to the binarizing comparator circuit 190 through thesimple-binarization/halftone mode selector circuit 196 depending on theof the mode select bit d₁ which forms part of the attribute signalS_(ATT) received from the attribute memory 212.

Each of these binary image signals generated in the binarizingcomparator circuit 190 responsive to the shaded digital image densitydata signals S_(SDD) is combined with the bit d₃ of the attribute signalS_(ATT) in a logic "AND" operation so that a binary image signal oflogic "1" or "0" state is generated in response to each of the shadeddigital image density data signals S_(SDD). Each of the binary imagesignals thus generated is further combined in a logic "AND" operationwith the simple binarization threshold signal S_(BT) output from thesimple binarization threshold generator circuit 192 or the halftonethreshold signal S_(HT) output from the halftone threshold signalgenerator circuit 194 with the result that a binary image signal S_(OUT)of logic "1" or "0" state is generated in respect of each of the shadeddigital image density data signals S_(SDD). The comparator circuit 190supplies the output signals S_(OUT) in non-inverted form to one inputterminal of the image signal output circuit 198 and in inverted form tothe other input terminal of the output circuit 198 through the inverter214.

Responsive to the white/black reversing bit d₂ of the attribute signalS_(ATT), the image signal output circuit 198 elects either thenon-inverted binary image signals S_(OUT) or the inverted versions ofthe signals S_(OUT) depending on the logic state of the white/blackreversing bit d₂. Each of the non-inverted binary image signals S_(OUT)or of the inverted versions of the signals S_(OUT) is combined with thevalid image area signal S_(VIA) of logic "1" or "0" state from thecentral processing unit 172 in a logic "AND" operation. The resultantbinary signals are delivered to a signal processing circuit of anyexternal output unit such as a printer or a display unit (not shown) toreproduce the image represented by the output signals from the signaloutput circuit 198.

FIG. 16 is a flowchart showing a main routine program to be executed bythe central processing unit 172 included in the control circuithereinbefore described with reference to FIG. 15.

The execution of the main routine program shown in FIG. 16 is startedwhen the apparatus is initially switched in. The main routine programstarts with step D01 at which the registers included in the centralprocessing unit 172 and the line memory 176 are reset. The step D01 isfollowed by step D02 to check for any command signal supplied from thecontrol panel 140B or from the editor module 200A. The command signal tobe checked for at this step D02 may be the signal S_(CMD) supplied fromany of the scan start key 142, common clear key 144, image scale-up andscale-down keys 148 and 150 and sheet size select keys 154 and 156, orthe character mode select signal S_(CM) supplied from the character modeselect key 158, the halftone mode select signal S_(HM) supplied from thehalftone mode select key 160, the density step-up signal S_(D1+) orS_(D1-) supplied from the character density "plus" or "minus" key 164aor 166a, or the density step-down signal S_(D2+) or S_(D2-) suppliedfrom the halftone density "plus" or "minus" key 164b or 166b. When theeditor communication grant key 206 is depressed, it is checked at stepD02 if there is a command signal supplied from any of the keys "F1" to"F7" on the editor module 200A. In the absence detected of any commandsignal supplied from the control panel 140B or from the editor module200A, the central processing unit 172 repeats the step D02 until it isfound that there is any command signal S_(CMD) received from the controlpanel 140B.

The central processing unit 172 proceeds to step D03 and executes a modeshift subroutine program if it is detected at step D02 that there is thesignal from the image scale-up or scale-down key 148 or 150, the signalfrom the sheet size select key 154 or 156, the character mode selectsignal S_(CM) from the character mode select key 158, the halftone modeselect signal S_(HM) from the halftone mode select key 160, the densitystep-up or step-down signal S_(D1+) or S_(D1-) from the characterdensity "plus" or "minus" key 164a or 166a, or the density step-up orstep-down signal S_(D2+) or S_(D2-) from the halftone density "plus" or"minus" key 164b or 166b. Responsive to any of these signals suppliedfrom the control panel 140B, the central processing unit 172 executesthe steps required by the supplied signal on condition that the mode ofoperation requested by the signal is validly acceptable in theapparatus. The details of this mode shift subroutine program D03 will behereinafter described with reference to FIG. 17.

On the other hand, if it is detected at step D02 that there is a commandsignal supplied from any of the keys "F1" to "F7" on the editor module200A, the central processing unit 172 proceeds to subroutine program D04and executes an attribute designation control subroutine program. Thedetails of this attribute designation control subroutine program D04will be hereinafter described with reference to FIG. 18.

If it is detected at step D02 that there is the signal supplied from thescan start key 142 on the control panel 140B, the central processingunit 172 proceeds to subroutine program D05 and executes an image readcontrol subroutine program. The details of this image read controlsubroutine program D05 will be hereinafter described with reference toFIGS. 19A and 19B.

FIG. 17 shows the details of a mode shift subroutine program D03included in the routine program hereinbefore described with reference toFIG. 16.

The mode shift subroutine program D03 starts with step E01 to check ifthe mode of operation requested by the command signal received from thecontrol panel 140B is validly acceptable in the apparatus and/or theexternal printer unit. If the answer for this step E01 is given in theaffirmative, the central processing unit 172 proceeds to step E02 toselect the requested mode of operation and thereafter reverts to themain routine program described with reference to FIG. 16 to check if anyother command signal is received from the control panel 140B or from theeditor module 200A. If it is determined at step E01 that the mode ofoperation requested by the command signal received from the controlpanel 140B is not validly acceptable and accordingly the answer for stepE01 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 16 to check if any other command signal is received from thecontrol panel 140B or from the editor module 200A.

The request for a mode of operation to be checked for at step E01 may bea request for any size of print output sheets from the sheet size selectkey 154 or 156, a request for the change of the reduction/magnificationratio from the image scale-up or scale-down key 148 or 150, a requestfor the simple binarization or halftone mode of image reading operationfrom the character mode select key 158 or the halftone mode select key160, or a request for the change of the density for image reading fromany of the density "plus" and "minus" keys 164a, 164b, 166a and 166b onthe control panel 140B. The steps E01 and E02 forming the mode shiftsubroutine program D03 herein shown are thus representative of thedetails similar to the steps B01 and B02 of the subroutine program A03hereinbefore described with reference to FIG. 11 and, as such, thefurther details of the subroutine program D03 will not be hereindescribed.

FIG. 18 shows the details of the attribute designation controlsubroutine program D04 also included in the main routine programhereinbefore described with reference to FIG. 16.

The attribute designation control subroutine program D04 starts withstep F01 to check if the attribute of image reading operation asrequested by the command signal received from the editor module 200A isvalidly acceptable in the apparatus and/or the external printer unit. Ifthe answer for this step F01 is given in the affirmative, the centralprocessing unit 172 proceeds to step F02 to select the requestedattribute of image reading operation and stores the data representativeof the selected attribute into the attribute memory 212 in the controlcircuit 170 described with reference to FIG. 15. The central processingunit 172 thereafter reverts to the main routine program described withreference to FIG. 16 to check if any other command signal is receivedfrom the control panel 140B or from the editor module 200A.

If it is determined at step F01 that the attribute of image readingoperation requested by the command signal received from the editormodule 200A is not validly acceptable and accordingly the answer forstep F01 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 16 to check if any other command signal is received from thecontrol panel 140B or from the editor module 200A.

The attribute of image reading operation to be checked for at step F01may be the whiting or blackening of the image outside or inside aspecified local area, the reversing of the white and black features ofan image, the establishment of the simple binarization or halftone modeof image reading operation, or the use of the first or second prescribeddither pattern for the halftone mode of image reading operation.

FIGS. 19A and 19B are flowcharts showing the details of the image readcontrol subroutine program D05 further included in the main routineprogram hereinbefore described with reference to FIG. 16. As has beennoted, the image read control subroutine program D05 is to be executedby the central processing unit 172 when if it is detected at step D02 inthe main routine program that there is present the signal supplied fromthe scan start key 142 on the control panel 140B, the central processingunit 172 executes the image read control subroutine program D04.

As shown in FIG. 19A, the image read control subroutine program D04starts with step G01 at which the central processing unit 172 suppliesthe control signal S_(EXP) to voltage regulator circuit 184 for theexposure lamp 106. Responsive to the signal S_(EXP) thus received fromthe central processing unit 172, the voltage regulator circuit 184outputs the lamp control voltage signal V_(EXP) to activate the exposurelamp 106 to illuminate. The central processing unit 172 then proceeds tostep G02 to fetch the data representing the valid density for imagereading from either the simple binarization mode density storage area210a or the halftone mode density storage area 210b of the internalmemory 210. The central processing unit 172 loads the data into thesimple binarization threshold generator circuit 192 as the simplebinarization image-density signal S_(BD) or into the halftone thresholdgenerator circuit 194 as the halftone image-density signal S_(HD).Responsive to the simple binarization image-density signal S_(BD) or thehalftone image-density signal S_(HD) thus supplied from the centralprocessing unit 172, the simple binarization threshold generator circuit192 outputs the simple binarization threshold signal S_(BT) indicativeof the fixed threshold value for use in the simple binarization mode ofimage reading operation, or the halftone threshold generator circuit 194outputs the stepwise variable halftone threshold signal S_(HT) for usein the halftone mode of image reading operation. The simple binarizationthreshold signal S_(BT) thus output from the simple binarizationthreshold generator circuit 192 or the halftone threshold signal S_(HT)output from the halftone threshold signal generator circuit 194 issupplied to the binarizing comparator circuit 190 through thesimple-binarization/halftone mode selector circuit 196 depending on thelogic state of the mode select bit d₁ which forms part of the attributesignal S_(ATT) received from the attribute memory 212.

The central processing unit 172 then proceeds to step G03 to check ifeach of the lamp/mirror carrier 118 and mirror carrier 120 is held in apredetermined home position with respect to the document support table102. This decision is made on the signal S_(POS) supplied from thedetecting means provided in association with each of the lamp/mirrorcarrier 118 and mirror carrier 120.

If it is found at this step G03 that the lamp/mirror carrier 118 andmirror carrier 120 are not held in their respective home positions, thecentral processing unit 172 proceeds to step G04 to supply the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step G05 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The loop of the steps G04 and G05 is repeateduntil it is confirmed at step G05 that the lamp/mirror and mirrorcarriers 118 and 120 have reached their respective home positions. Whenit is thus found at step G05 that the carriers 118 and 120 have reachedtheir respective home positions and accordingly the answer for the stepG05 turns affirmative, the central processing unit 172 proceeds to stepG06 to reset the signal S_(MD1) and stop the scanner drive motor 132.

Subsequently to this step G06 or when it is confirmed at step G05 thatthe lamp/mirror and mirror carriers 118 and 120 are held in theirrespective home positions, the central processing unit 172 proceeds tostep G07 to supply the motor actuation signal S_(MD1) for a second timeto the motor driver circuit 178 for the scanner drive motor 132.Responsive to the motor actuation signal S_(MD1) thus received from thecentral processing unit 172, the motor driver circuit 178 actuates thescanner drive motor 132 into operation to move the lamp/mirror andmirror carriers 118 and 120 forwardly from their home positions in thedirections indicated by arrowheads a and b in FIG. 1. The document Dplaced on the document support table 102 is now optically scanned by theexposure lamp 106 and the resultant image-bearing beam of light B isdirected past the reflector mirrors 110, 112 and 114 to the image sensor122.

The step G07 is followed by step G08 at which the central processingunit 172 reads the shading data correcting pattern detected from thelower face of the document scale 104 and stored in the line memory 176.On the basis of the shading data correcting pattern read from the linememory 176, the central processing unit 172 formulates the data inaccordance with which shading signals are to be generated in the shadingcircuit 188. The data thus generated in the central processing unit 172is stored into the line memory 176.

The central processing unit 172 then detects at step G09 whether or notthe lamp/mirror carrier 118 and mirror carrier 120 have reached thepositions effective to scan the leading end of the document D placed onthe document support table 102. The step G09 is repeated until it isconfirmed that the document D on the document support table 102 isscanned at its leading end. When it is thus determined at step G09 thatthe document D on the document support table 102 is scanned at itsleading end and accordingly the answer for the step G09 turnsaffirmative, the central processing unit 172 proceeds to step G10 (FIG.19B) to generate the valid image area signal S_(VIA). The valid imagearea signal S_(VIA) thus generated by the central processing unit 172 atstep G10 is supplied to the control terminal of the image signal outputcircuit 198.

The central processing unit 172 then proceeds to step G11 to instructthe attribute memory 212 to distribute the bits d₃ to d₀ of theattribute signal S_(ATT) to the binarizing comparator circuit 190, imagesignal output circuit 198, mode selector circuit 196 and halftone modethreshold generator 194. The image density data represented by theshaded digital image density data signals S_(SDD) output from theshading generator circuit 188 are thus processed in the binarizingcomparator circuit 190 on the basis of the bits d₃, d₁ and d₀ of theattribute signal S_(ATT) and further in the image signal output circuit198 on the basis of the bit d₂ of the attribute signal S_(ATT).

Subsequently to step G11, the central processing unit 172 detects atstep G12 whether or not the lamp/mirror carrier 118 and mirror carrier120 have reached the positions effective to scan the trailing end of thedocument D on the document support table 102. The step G12 is repeateduntil it is confirmed that the document D on the document support table102 has been scanned to its trailing end. When it is thus determined atstep G12 that the scanning of the document D on the document supporttable 102 is complete and accordingly the answer for the step G12 turnsaffirmative, the central processing unit 172 proceeds to step G13 toreset the valid image area signal S_(VIA) which has been supplied to thecontrol terminal of the image signal output circuit 198.

The central processing unit 172 then proceeds to step G14 to cease thesupply of the control signal S_(EXP) to the voltage regulator circuit184 to de-activate the exposure lamp 106. The step G14 is followed bystep G15 at which the central processing unit 172 supplies the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/ mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step G16 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The step G16 is repeated until it isconfirmed that the lamp/mirror and mirror carriers 118 and 120 havereached their respective home positions. When it is thus found at stepG16 that the carriers 118 and 120 have reached their respective homepositions and accordingly the answer for the step G16 turns affirmative,the central processing unit 172 proceeds to step G17 to reset the signalS_(MD1) and stop the scanner drive motor 132. Subsequently, the centralprocessing unit 172 reverts to the main routine program described withreference to FIG. 16 to check if any other command signal is receivedfrom the control panel 140B or from the editor module 140A.

Third Preferred Embodiment (FIGS. 20 to 24)

Description will be hereinafter made in regard to a third preferredembodiment of an image reading apparatus according to the presentinvention. The third preferred embodiment of the present invention is amodification of the second preferred embodiment of the invention and isthus also characterized by the capabilities to designate a particularlocal area within a document and read the image in the particular areain a desired mode of image reading operation. In the third preferredembodiment of the present invention is used the control panel 140Bdescribed with reference to FIG. 14 in addition to the mechanical andoptical arrangement described with reference to FIG. 1.

FIG. 20 shows an editor module 200B for use in the third preferredembodiment of the present invention. Similarly to its counterpart in thesecond preferred embodiment of the present invention, the editor module200B herein shown largely consists of a tablet section 202 and a keysection 204 comprising a total of nine control keys. The tablet section202 of the editor module 200B is used in combination with a light pen todefine a desired local area within the image-carrying document to bereproduced. As has been noted with reference to FIG. 13, a square-shapedrectangular area of a document D such as the area "A1" or the area "A2"herein indicated by phantom lines can be defined simply by specifyingthe locations of the opposite ends of one of the diagonals of the area"A1" or the area "A2" with use of a light pen.

The control keys provided in the key section 204 of the editor module200B include a trimming key "F1", a masking key "F2", a white/blackreverse key "F3", a simple binarization mode select key "F4", a firstdither-pattern halftone mode select key "F5", a second dither-patternhalftone mode select key "F6", and a trim/mask cancel key "F7". Thefunctions achievable through use of these keys "F1" to "F7" are similarto those of their respective equivalents provided in the editor module200A described with reference to FIG. 13. In the key section 204 of theeditor module 200B are further provided a data-clear key "C" and adata-send key "S", which are also similar to their respectiveequivalents provided in the editor module 200A shown in FIG. 13.

In the key section 204 of the editor module 200B used in the thirdpreferred embodiment of the present invention are provided additionalcontrol keys which include an image editing key "E", a density controlkey "D", a simple binarization density key "SB", a halftone density key"HT", a density "plus" key 216, and a density "minus" key 218. Thedensity "plus" and "minus" keys 216 and 218 are respectively provided topermit entry of instructions from the editor module 200B to increase anddecrease the valid degree of lightness for image reading. In associationwith these density "plus" and "minus" keys 216 and 218 is provided adensity indicator section 220 consisting of a series of subsectionsarranged in the order of lightness indicated by numerals "1" to "9". Thesubsection indicating the selected density for image reading is to behighlighted with the highlight stepwise moved in one direction along theindicator section 220 each time the density "plus" key 216 is depressedor in the opposite direction along the indicator section 220 each timethe density "minus" key 218 is depressed by the operator.

The image editing key "E" is used to enter an instruction to select themodes of operation designated through the keys "F1" to "F7" in respectof the designated local area "A1" or "A2" of the document D. The densitycontrol key "D" is used to enter an instruction that the image densityfor the specified local area "A1" or "A2" of the document D is to bedesignated from the density "plus" key 216 or from the density "minus"key 218. The simple binarization density key "SB" is used to enter aninstruction that the simple binarization mode of image reading operationis to be selected for the image density designated or to be designatedthrough use of the density "plus" or "minus" key 216 or 218. Likewise,the halftone density key "HT" is used to enter an instruction that thehalftone mode of image reading operation is to be selected for the imagedensity designated or to be designated through use of the density "plus"or "minus" key 216 or 218.

In the third preferred embodiment of the present invention, theoperator's desired mode of operation can be selected either from thecontrol panel 140B shown in FIG. 9 or from the editor module 200B shownin FIG. 20.

When it is desired that the control panel 140B shown in FIG. 9 be usedfor the entry of instructions to select the desired modes of operation,it is first confirmed if the editor communication grant key 206 has beendepressed to enter an instruction to grant reception of data andcommands from the editor module 200B. If it is found that the key 206has been depressed, the key 206 is depressed for a second time to cancelsuch an instruction. After the instruction is thus cancelled, the simplebinarization density key "SB" may be depressed to enter an instructionto select the simple binarization mode of image reading operation beforethe desired density for image reading is designated through use of thedensity "plus" or "minus" key 216 or 218. Alternatively, the halftonedensity key "HT" may be depressed after the instruction is cancelled sothat an instruction is entered to select the halftone mode of imagereading operation before the desired density for image reading isdesignated through use of the density "plus" or "minus" key 216 or 218.

On the other hand, when it is desired that the editor module 200B shownin FIG. 20 be used for the entry of instructions to select the desiredmodes of operation, the editor communication grant key 206 is depressedto enter an instruction to grant reception of data and commands from theeditor module 200B. After such an instruction is entered, the functionsto be used for the edited mode of image reading operation may beselected from the keys "F1" to "F7" or the density for image reading maybe designated from the density "plus" or "minus" key 216 or 218 on theeditor module 200B.

If it is desired that the functions to be used for the edited mode ofimage reading operation be selected from the keys "F1" to "F7", theimage editing key "E" on the editor module 200B is depressed prior toselection of the functions to inform that the functions to be used forthe edited mode of image reading operation are to be selected from thekeys "F1" to "F7". After the image editing key "E" is thus depressed, adesired local area of the document D on the tablet section 202 such asthe area "A1" or "A2" as shown in FIG. 20 is designated by specifyingthe locations of a diagonal of the area area "A1" or "A2" with use of alight pen. Any one or ones of the keys "F1" to "F7" may then bedepressed to select the functions to be used for the edited mode ofimage reading operation to be carried out for the specified local area"A1" or "A2" of the document D on the tablet section 202. The data-sendkey "S" may be thereafter depressed to enter an instruction to transmitto the control circuit of the apparatus the data and commands generatedthrough manipulation of any of the keys on the editor module 200B forthe specified local area "A1" or "A2" of the document D placed on thetablet section 202.

On the other hand, if it is desired that the density for image readingbe designated from the density "plus" or "minus" key 216 or 218, thedensity control key "D" on the editor module 200B is depressed prior toselection of the density for image reading to inform that the imagereading density to be used for the edited mode of image readingoperation is to be designated from the key 216 or 218. After the densitycontrol key "D" is thus depressed, a desired local area of the documentD on the tablet section 202 such as the area "A1" or "A2" as shown inFIG. 20 is designated by specifying the locations of a diagonal of thearea area "A1" or "A2" with use of a light pen. The image density to beused for the reading of the image in the specified local area "A1" or"A2" of the document D is then designated through use of the density"plus" key 216 or the density "minus" key 218. Thereafter, either thesimple binarization density key "SB" or the halftone density key "HT" isdepressed to enter an instruction that the simple binarization orhalftone mode of image reading operation is to be selected for the imagedensity which has been designated through use of the density "plus" or"minus" key 216 or 218. The data-send key "S" may be thereafterdepressed to enter an instruction to transmit to the control circuit ofthe apparatus the data and commands generated through manipulation ofany of the keys on the editor module 200B for the specified local area"A1" or "A2" of the document D placed on the tablet section 202.

FIG. 21 shows the general construction and arrangement of a controlcircuit 170C for use in the third preferred embodiment of an imagereading apparatus according to the present invention. The controlcircuit 170C for use in the third preferred embodiment of the presentinvention is essentially similar to the control circuit 170B of thesecond preferred embodiment of the present invention. In the controlcircuit 170C herein shown, the central processing unit 172 is thusresponsive not only to the various command signals supplied from thecontrol panel 140B but to various data and command signals S_(ED)generated in and supplied from the editor module 200B hereinbeforedescribed with reference to FIG. 20. It may be noted that the data andcommand signals S_(ED) supplied from the editor module 200B in the thirdpreferred embodiment of the present invention include not only thecommand signals generated by any of the keys "F1" to "F7", "C" and "S"as in the first preferred embodiment of the present invention but alsothe command signals which may be generated by any of the image editingkey "E", density control key "D", simple binarization density key "SB",halftone density key "HT", density "plus" key 216, and density "minus"key 218 provided on the editor module 200B. As has been noted in regardto the second preferred embodiment of the present invention, the dataand command signals generated by any of these keys on the editor module200B are accepted by the central processing unit 172 only when theeditor communication grant key 206 is depressed and are invalidated whenthe key 206 is depressed after the key was once depressed.

In the control circuit 170C illustrated in FIG. 21, the centralprocessing unit 172 has incorporated therein an internal memory 210having a simple binarization mode density storage area 210a and ahalftone mode density storage area 210b, as shown. Thus, when the validdensity for image reading is designated from the character density"plus" or "minus" key 164a or 166a with the simple binarization mode ofimage reading operation selected from the character mode select key 158on the control panel 140B, the data representing the density is storedinto the simple binarization mode density storage area 210a of theinternal memory 210. On the other hand, when the valid density for imagereading is designated from the halftone density "plus" or "minus" key164b or 166b with the halftone mode of image reading operation selectedfrom the halftone mode select key 160 on the control panel 140B, thedata representing the density is stored into the halftone mode densitystorage area 210b of the internal memory 210.

Responsive to the data and command signals S_(ED) supplied from theeditor module 200B and/or to the signal supplied from any of the density"plus" and "minus" keys 164a, 164b, 166a and 166b on the control panel140B, the central processing unit 172 generates a twelve-bit attributesignal S_(ATT) indicative of selected ones of the attributes of imagereading operation. The attribute signal S_(ATT) thus representative ofthe selected attributes of image reading operation is supplied to andstored into an attribute memory 212 implemented by a semiconductorrandom-access. Fractions of the signal S_(ATT) thus stored into theattribute memory 212 are supplied to the comparator circuit 190, simplebinarization threshold generator circuit 192, halftone thresholdgenerator circuit 194, simple-binarization/halftone mode selectorcircuit 196, and image signal output circuit 198 as will be described inmore detail.

The image signal output circuit 198 used in the control circuit 170Cillustrated in FIG. 21 also has two input terminals one of which isconnected directly to the output terminal of the comparator circuit 190and the other of which is connected through an inverter 214 to theoutput terminal of the comparator circuit 190 The binary image signalsS_(OUT) produced by the comparator circuit 190 responsive to the shadeddigital image density data signals S_(SDD) from the shading circuit 188are thus supplied in non-inverted form to one input terminal of theoutput circuit 198 and in inverted form to the other input terminal ofthe output circuit 198.

The signal S_(ATT) to be generated by the central processing unit 172and stored into the attribute memory 212 is indicative of twelvedifferent kinds of attributes in respect of an image pixel having a unitarea measuring 1 mm by 1 mm and is provided in the form of a sequence oftwelve bits d₁₁ to d₀ each of logic "1" or "0" state.

The upper four bits d₁₁ to d₈ of the attribute signal S_(ATT) provide afirst fraction of the signal S_(ATT) and specify the image density foruse in the halftone mode of image reading operation. The image densityto be specified by the bits d₁₁ to d₈ of the attribute signal S_(ATT)may be any one of the nine different image densities "1" to "9" assignedto the individual subsections, respectively, of the density indicatorsection 220 of the editor module 200B. The first fraction of theattribute signal S_(ATT) thus provided by the upper four bits d₁₁ to d₈of the signal S_(ATT) is supplied to the halftone mode thresholdgenerator circuit 194 and designates one of the nine different imagedensities "1" to "9" to be used in the halftone mode of image readingoperation.

The intermediate four bits d₇ to d₄ of the attribute signal S_(ATT)provide a second fraction of the signal S_(ATT) and specify the imagedensity for use in the simple binarization mode of image readingoperation. The image density to be specified by the bits d₇ to d₄ of theattribute signal S_(ATT) may also be any one of the nine different imagedensities "1" to "9" assigned to the individual subsections,respectively, of the density indicator section 220 of the editor module200B. The second fraction of the attribute signal S_(ATT) thus providedby the intermediate four bits d₇ to d₄ of the signal S_(ATT) is suppliedto the simple binarization mode threshold generator circuit 192 anddesignates one of the nine different image densities "1" to "9" to beused in the simple binarization mode of image reading operation.

The remaining lower four bits d₃ to d₀ of the attribute signal S_(ATT)provide third to sixth fractions, respectively, of the signal S_(ATT)and are similar to their respective equivalents of the attribute signalS_(ATT) used in the control circuit 170B of the second preferredembodiment of the present invention as hereinbefore described withreference to FIG. 15.

Thus, the bit d₃ of the attribute signal S_(ATT) providing the thirdfraction of the signal S_(ATT) indicates selection of the blanking outof an image pixel when set to logic "0" state and selection of thenon-blanking of a pixel when set to logic "1" state. The third fractionof the attribute signal S_(ATT) thus provided by the bit d₃ of thesignal S_(ATT) is supplied to the control terminal of the comparatorcircuit 190 and, when the bit d₃ is set to logic "0" state, enables thecomparator circuit 190 to white out the specified image pixel (orblacken out the pixel in the presence of the white/black reversing bitd₂ of logic "1" state).

The bit d₂ of the attribute signal S_(ATT) providing the fourth fractionof the signal S_(ATT) indicates selection of the non-reversing of thewhite and black features of an image when set to logic "0" state andselection of the reversing of the white and black features of an imagewhen set to logic "1" state. The fourth fraction of the attribute signalS_(ATT) thus provided by the bit d₂ of the signal S_(ATT) is supplied toone control terminal of the image signal output circuit 198. To anothercontrol terminal of the image signal output circuit 198 is supplied avalid image area signal S_(VIA) of logic "1" or "0" state from thecentral processing unit 172. Thus, the image signal output circuit 198in the control circuit 170C of the third preferred embodiment of thepresent invention also receives the binary image signals S_(OUT)supplied both in inverted and non-inverted forms from the comparatorcircuit 190, the bit d₂ of the attribute signal S_(ATT) supplied fromthe attribute memory 212, and the valid image area signal S_(VIA)supplied from the central processing unit 172.

The bit d₁ of the attribute signal S_(ATT) providing the fifth fractionof the signal S_(ATT) indicates selection of the simple binarizationmode of image reading operation when set to logic "0" state andselection of the halftone mode of image reading operation when set tologic "1" state. The fifth fraction of the attribute signal S_(ATT) thusprovided by the bit d₁ of the signal S_(ATT) is supplied to the controlterminal of the simple-binarization/halftone mode selector circuit 196.Responsive to this mode select bit d₁, the simple-binarization/halftonemode selector circuit 196 supplies either the simple binarizationthreshold signal S_(BT) or the halftone threshold signal S_(HD)depending on the logic state of the bit d₁.

The bit d₀ of the attribute signal S_(ATT) providing the sixth fractionof the signal S_(ATT) indicates selection of the first prescribed ditherpattern simple binarization when set to logic "0" state and selection ofthe the second dither when set to logic "1" state. The sixth fraction ofthe attribute signal S_(ATT) thus provided by the bit d₀ of the signalS_(ATT) is supplied to the halftone threshold generator circuit 194,which is thus enabled to select the first or second prescribed ditherpattern depending on the logic state of the bit d₀.

While the bits d₃, d₂ and d₀ of the attribute signal S_(ATT) used in thesecond preferred embodiment of the present invention are to be generatedexclusively responsive to command signal supplied from the editor module200B, the other bits d₁₁ to d₄ and d₁ of the attribute signal S_(ATT)may be generated either responsive to command signals supplied from theeditor module 200B or responsive to command signals supplied from thecontrol panel 200B described with reference to FIG. 14. The centralprocessing unit 172 responsive to command signals supplied from theeditor module 200B is enabled to generate the bits d₁₁ to d₄ and d₁ ofthe attribute signal S_(ATT) on condition that the editor communicationgrant key 206 is depressed to grant transmission of data and commandsignals from the editor module 200 to the central processing unit 172.Any data and command signals which may be produced in the editor modulewill be invalidated when the key 206 is depressed for a second time.

When the editor communication grant key 206 is depressed so thattransmission of data and command signals from the editor module 200 tothe central processing unit 172, the upper four bits d₁₁ to d₈ of theattribute signal S_(ATT) are generated in response to the signalsproduced by depression of the density control key "D", the halftonedensity key "HT", and one of the density "plus" and "minus" keys 216 and218 on the editor module 200B. The data representing the bits d₁₁ to d₈thus generated by the central processing unit 172 are stored into thehalftone mode density storage area 210b of the internal memory 210. Theintermediate four bits d₇ to d₄ of the attribute signal S_(ATT) aregenerated by the central processing unit 172 in response to the signalsproduced by depression of the density control key "D", the simplebinarization density key "SB", and one of the density "plus" and "minus"keys 216 and 218. The data representing the bits d₇ to d₄ thus generatedby the central processing unit 172 are stored into the simplebinarization mode density storage area 210a of the internal memory 210.

Of the remaining lower four bits d₃ to d₀ of the attribute signalS_(ATT), the bit d₃ is set to logic "0" state when the trimming key "F1"or the masking key "F2" on the editor module 200B is depressed, and thebit d₂ is set to logic "1" state when the white/black reverse key "F3"on the editor module 200B is depressed. The bit d₁ of the attributesignal S_(ATT) is set to logic "0" state when the simple binarizationmode select key "F4" on the editor module 200B is depressed, and the bitd₀ of the attribute signal S_(ATT) is set to logic "0" state when thefirst dither-pattern halftone mode select key "F5" on the editor module200B is depressed and is set to logic "1" state when the seconddither-pattern halftone mode select key "F6" on the editor module 200Bis depressed.

On the other hand, when the editor communication grant key 206 which hasonce been depressed is depressed for a second time, transmission of dataand command signals from the editor module 200A to the centralprocessing unit 172 is prohibited so that the central processing unit172 is qualified to generate the bits d₁₁ to d₄ and d₀ of the attributesignal S_(ATT) in response to data and command signals produced by anyof the keys provided on the control panel 140B described with referenceto FIG. 9.

In this instance, the upper four bits d₁₁ to d₈ of the attribute signalS_(ATT) are generated in response to the density step-up signal S_(D2+)produced by depression of the halftone density "plus" key 164b or thedensity step-down signal S_(D2-) produced by depression of the halftonedensity "minus" key 166b in the presence of the halftone mode selectsignal S_(HM) produced by depression of the halftone mode select key 160on the control panel 140B. The data representing the bits d₁₁ to d₈ thusgenerated by the central processing unit 172 are stored into thehalftone mode density storage area 210b of the internal memory 210. Theintermediate four bits d₇ to d₄ of the attribute signal S_(ATT) aregenerated by the central processing unit 172 in response to the densitystep-up signal S_(D1+) produced by depression of the character density"plus" key 164a or the density step-down signal S_(D1-) produced bydepression of the character density "minus" key 166a in the presence ofthe character mode select signal S_(CM) produced by depression of thecharacter mode select key 158 on the control panel 140B. The datarepresenting the bits d₇ to d₄ thus generated by the central processingunit 172 are stored into the character mode density storage area 210a ofthe internal memory 210.

On the other hand, the bit d₁ of the attribute signal S_(ATT) is set tologic "0" state when the character mode select key 158 on the controlpanel 140B is depressed and to logic "1" state when the halftone modeselect key 160 on the control panel 140B is depressed. When transmissionof data and command signals from the editor module 200A to the centralprocessing unit 172 is prohibited with the editor communication grantkey 206 depressed after the key 206 was once depressed, the remainingbits d₃, d₂ and d₀ of the attribute signal S_(ATT) are set to the logicstates assigned to the standard modes of operation predetermined bydefault rules and could not be varied from the control panel 140B. Thesestandard modes of operation represented by the bits d₃, d₂ and d₀ ofsuch logic states are the non-blanking of a pixel represented by the bitd₃ of logic "1" state, the non-reversing of the white and black featuresof an image represented by the bit d₂ of logic "0" state, and the firstprescribed dither pattern simple binarization represented by the bit d₀of logic "0".

As in the control circuit 170B of the second preferred embodiment of thepresent invention, the image density data in the form of the shadeddigital image density data signals S_(SDD) supplied to the comparatorcircuit 190 is compared with the simple binarization threshold signalS_(BT) supplied from the simple binarization threshold generator circuit192 or with the halftone image-density signal S_(HD) supplied from thehalftone threshold signal generator circuit 194 through thesimple-binarization/halftone mode selector circuit 196. The comparatorcircuit 190 is thus operative to generate binary image signals each oflogic "1" or "0" state responsive to the shaded digital image densitydata signals S_(SDD).

In the meantime, the data representing the valid density for imagereading is stored in the simple binarization mode density storage area210a or the halftone mode density storage area 210b of the internalmemory 210 of the central processing unit 172. As has been noted, thisdata has been originally generated on the basis of the command signalsproduced by the density "plus" key 216 or the density "minus" key 218 onthe editor module 200B or the command signals produced by the density"plus" key 164a or 164b or the density "minus" key 166b or 166b on thecontrol panel 140B. The central processing unit 172 formulates theattribute signal S_(ATT) on the basis of the data thus stored in thesimple binarization or halftone mode density storage area 210a or 210bof the internal memory 210 of the central processing unit 172 and loadthe signal S_(ATT) into the attribute memory 212. The attribute memory212 then distributes the bits d₁₁ to d₈ and d₀ to the halftone thresholdgenerator circuit 194, the bits d₇ to d₄ to the simple binarizationthreshold generator circuit 192, the bit d₃ to the comparator circuit190, the bit d₂ to the image signal output circuit 198, and the bit d₁to the simple-binarization/halftone mode selector circuit 196 as hasbeen described.

Responsive to the bits d₇ to d₄ of the attribute signal S_(ATT) or thebits d₁₁ to d₈ and d₀ of the attribute signal S_(ATT) thus supplied fromthe central processing unit 172, the simple binarization thresholdgenerator circuit 192 outputs the simple binarization threshold signalS_(BT) indicative of a stepwise variable threshold value for use in thesimple binarization mode of image reading operation, or the halftonethreshold generator circuit 194 outputs the halftone threshold signalS_(HT) indicative of a stepwise variable threshold value for use in thehalftone mode of image reading operation. The halftone threshold signalS_(HT) output from the halftone threshold generator circuit 194 isstepwise variable in accordance with the first or second dither patterndepending on the logic state of the bit d₀ of the attribute signalS_(ATT). The simple binarization threshold signal S_(BT) thus outputfrom the simple binarization threshold generator circuit 192 or thehalftone threshold signal S_(HT) output from the halftone thresholdsignal generator circuit 194 is supplied to the comparator circuit 190through the simple-binarization/halftone mode selector circuit 196depending on the logic state of the mode select bit d₁ which forms partof the attribute signal S_(ATT) received from the attribute memory 212.

Each of these binary image signals generated in the comparator circuit190 responsive to the shaded digital image density data signals S_(SDD)is combined with the bit d₃ of the attribute signal S_(ATT) in a logic"AND" operation so that a binary image signal of logic "1" or "0" stateis generated in response to each of the shaded digital image densitydata signals S_(SDD). Each of the binary image signals thus generated isfurther combined in a logic "AND" operation with the simple binarizationthreshold signal S_(BT) output from the simple binarization thresholdgenerator circuit 192 or the halftone threshold signal S_(HT) outputfrom the halftone threshold signal generator circuit 194 with the resultthat a binary image signal S_(OUT) of logic "1" or "0" state isgenerated in respect of each of the shaded digital image density datasignals S_(SDD). The comparator circuit 190 supplies the output signalsS_(OUT) in non-inverted form to one input terminal of the image signaloutput circuit 198 and in inverted form to the other input terminal ofthe output circuit 198 through the inverter 214.

Responsive to the white/black reversing bit d₂ of the attribute signalS_(ATT), the image signal output circuit 198 elects either thenon-inverted binary image signals S_(OUT) or the inverted versions ofthe signals S_(OUT) depending on the logic state of the white/blackreversing bit d₂. Each of the non-inverted binary image signals S_(OUT)or of the inverted versions of the signals S_(OUT) is combined with thevalid image area signal S_(VIA) of logic "1" or "0" state from thecentral processing unit 172 in a logic "AND" operation. The resultantbinary signals are delivered to a signal processing circuit of anyexternal output unit such as a printer or a display unit (not shown) toreproduce the image represented by the output signals from the signaloutput circuit 198.

FIG. 22 is a flowchart showing a main routine program to be executed bythe central processing unit 172 included in the control circuithereinbefore described with reference to FIG. 21.

The execution of the main routine program shown in FIG. 22 is startedwhen the apparatus is initially switched in. The main routine programstarts with step H01 at which the registers included in the centralprocessing unit 172 and the line memory 176 are reset. The step H01 isfollowed by step H02 to check for any command signal supplied from thecontrol panel 140B (FIG. 14). The command signal to be checked for atthis step H02 may be the signal S_(CMD) supplied from any of the scanstart key 142, common clear key 144, image scale-up and scale-down keys148 and 150 and sheet size select keys 154 and 156, or the charactermode select signal S_(CM) supplied from the character mode select key158, the halftone mode select signal S_(HM) supplied from the halftonemode select key 160, the density step-up signal S_(D1+) or S_(D1-)supplied from the character density "plus" or "minus" key 164a 166a, orthe density step-down signal S_(D2+) or S_(D2-) supplied from thehalftone density "plus" or "minus" key 164b or 166b. When the editorcommunication grant key 206 is depressed on the control panel 140B, itis checked at step H02 if there is a command signal supplied from any ofthe keys "F1" to "F7", "E", "D", "SB" and "HT" on the editor module200B. In the absence detected of any command signal supplied from thecontrol panel 140B or the editor module 200B, the central processingunit 172 repeats the step H02 until it is found that there is anycommand signal S_(CMD) received from the control panel 140B.

The central processing unit 172 proceeds to step H03 and executes a modeshift subroutine program if it is detected at step H02 that there is thesignal from the image scale-up or scale-down key 148 or 150, the signalfrom the sheet size select key 154 or 156, the character mode selectsignal S_(CM) from the character mode select key 158, the halftone modeselect signal S_(HM) from the halftone mode select key 160, the densitystep-up or step-down signal S_(D1+) or S_(D1-) from the characterdensity "plus" or "minus" key 164a or 166a, or the density step-up orstep-down signal S_(D2+) or S_(D2-) from the halftone density "plus" or"minus" key 164b or 166b. Responsive to any of these signals suppliedfrom the control panel 140B, the central processing unit 172 executesthe steps required by the supplied signal on condition that the mode ofoperation requested by the signal is validly acceptable in theapparatus. The details of this mode shift subroutine program H03 will behereinafter described with reference to FIG. 23.

On the other hand, if it is detected at step H02 that there is a commandsignal supplied from any of the keys "F1" to "F7" on the editor module200B, the central processing unit 172 proceeds to subroutine program H04and executes an area attribute designation control subroutine program.The central processing unit 172 is enabled to execute this areaattribute designation control subroutine program H04 when, and onlywhen, the editor communication grant key 206 on the control panel 140Bis depressed to grant transmission of data and command signals from theeditor module 200 to the central processing unit 172. The details of thearea attribute designation control subroutine program H04 will behereinafter described with reference to FIG. 24.

If it is detected at step H02 that there is the signal supplied from thescan start key 142 on the control panel 140B, the central processingunit 172 proceeds to subroutine program H05 and executes an image readcontrol subroutine program. The details of this image read controlsubroutine program H05 are essentially similar to those which have beendescribed with reference to FIGS. 19A and 19B in regard to the secondpreferred embodiment of the present invention and, as such, will not beherein described.

FIG. 23 shows the details of the mode shift subroutine program H03included in the routine program hereinbefore described with reference toFIG. 22.

The mode shift subroutine program H03 starts with step I01 to determinewhich command signal is received from the control panel 140B. Thus, ifit is detected at step I01 that there is the signal received from thesheet size select key 154 or 156, the central processing unit 172proceeds to step I02 to check if the request for the size of printoutput sheets designated by the signal received is validly acceptable inthe apparatus and/or the external printer unit. If the answer for thisstep I02 is given in the affirmative, the central processing unit 172proceeds to step I03 to select the size of print output sheetsdesignated by the signal received and thereafter reverts to the mainroutine program described with reference to FIG. 22 to check if anyother command signal is received from the control panel 140B or theeditor module 200B. If it is determined at step I02 that the request forthe size of print output sheets designated by the signal received is notvalidly acceptable and accordingly the answer for step I02 is given inthe negative, the central processing unit 172 immediately reverts to themain routine program described with reference to FIG. 22 to check if anyother command signal is received from the control panel 140B or theeditor module 200B.

If it is detected at step I01 that there is the signal received from theimage scale-up or scale-down key 148 or 150, the central processing unit172 proceeds to step I04 to check if the request for thereduction/magnification ratio designated by the signal received isvalidly acceptable in the apparatus and/or the external printer unit. Ifthe answer for this step I04 is given in the affirmative, the centralprocessing unit 172 proceeds to step I05 to select thereduction/magnification ratio designated by the signal received andthereafter reverts to the main routine program described with referenceto FIG. 22 to check if any other command signal is received from thecontrol panel 140B or the editor module 140B. If it is determined atstep I04 that the request for the reduction/magnification ratiodesignated by the signal received is not validly acceptable andaccordingly the answer for step I04 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 22 to check if any othercommand signal is received from the control panel 140B or the editormodule 200B.

If it is detected at step I01 that there is the character mode selectsignal S_(CM) received from the character mode select key 158 or thehalftone mode select signal S_(HM) received from the halftone modeselect key 160, the central processing unit 172 proceeds to step I06 tocheck if the request for the simple binarization or halftone mode ofimage reading operation requested by the signal S_(CM) or S_(HM)received is validly acceptable in the apparatus. If the answer for thisstep I06 is given in the affirmative, the central processing unit 172proceeds to step I07 to select the simple binarization or halftone modeof image reading operation requested by the signal S_(CM) or S_(HM)received and sets the bit d₁ of the attribute signal S_(ATT) to logic"0" state or logic "1" state, respectively, for each of all the pixelsto be reproduced. The bit d₁ thus set to logic "0" or "1" state andrepresentative of the simple binarization or halftone mode of imagereading operation as the selected attribute of the image readingoperation to be performed is stored into the attribute memory 212 in thecontrol circuit 170C. It may be herein noted that each of the bits d₃,d₂ and d₀ of the attribute signal S_(ATT) is set to the logic stateassigned to the predetermined standard mode of operation since thetransmission of data and command signals from the editor module 200A tothe central processing unit 172 is currently prohibited with the editorcommunication grant key 206 depressed after the key 206 was oncedepressed. Subsequently to step I07, the central processing unit 172reverts to the main routine program described with reference to FIG. 22to check if any other command signal is received from the control panel140B or the editor module 200B.

If it is determined at step I06 that the request for the mode of imagereading operation requested by the character or halftone mode selectsignal S_(CM) or S_(HM) received is not validly acceptable andaccordingly the answer for step I06 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 22 to check if any othercommand signal is received from the control panel 140B or the editormodule 200B.

If it is detected at step I01 that there is the density step-up signalS_(D1+) or S_(D2+) received from the density "plus" key 164a or 164b orthere is the density step-down signal S_(D1-) or S_(D2-) received fromthe density "minus" key 166a or 166b on the control panel 140B, thecentral processing unit 172 proceeds to step I08 to check if there isthe character mode select signal S_(CM) received from the character modeselect key 158 on the control panel 140B. If the answer for this stepI08 is given in the affirmative, the central processing unit 172proceeds to step I09 to check if the request for the density for imagereading designated by the signal S_(D1+) or S_(D1-) or the signalS_(D2+) or S_(D2-) received is validly acceptable in the simplebinarization mode of image reading operation. If the answer for thisstep I09 is given in the affirmative, the central processing unit 172proceeds to step I10 to select the density for image reading designatedby the signal S_(D1+) or S_(D1-) or the signal S_(D2+) or S_(D2-)received for the selected simple binarization mode of image readingoperation. The central processing unit 172 thus sets the bits d₇ to d₄of the attribute signal S_(ATT) to logic "0" and/or "1" states for eachof all the pixels to be reproduced. The bits d₇ to d₄ thus set to logic"0" and/or "1" states and representative any of the nine differentdensities "1" to "9" available in the simple binarization mode of imagereading operation are also stored into the attribute memory 212 in thecontrol circuit 170C. Subsequently to the step I10, the centralprocessing unit 172 reverts to the main routine program described withreference to FIG. 22 to check if any other command signal is receivedfrom the control panel 140B or the editor module 200B.

If it is determined at step I08 that there is not the character modeselect signal S_(CM) received from the character mode select key 158 andas such the answer for step I08 is given in the negative, the centralprocessing unit 172 proceeds to step I11 to check if the request for thedensity for image reading designated by the signal S_(D1+) or S_(D1-) orthe signal S_(D2+) or S_(D2-) received for the selected simplebinarization mode of image reading operation is validly acceptable inthe halftone mode of image reading operation. If the answer for thisstep I11 is given in the affirmative, the central processing unit 172proceeds to step I12 to select the density for image reading designatedby the signal S_(D1+) or S_(D1-) or the signal S_(D2+) or S_(D2-)received for the selected halftone mode of image reading operation andsets the bits d₁₁ to d₈ of the attribute signal S_(ATT) to logic "0"and/or "1" states for each of all the pixels to be reproduced. The bitsd₁₁ to d₈ thus set to logic "0" and/or "1" states and representative anyof the nine different densities "1" to "9" available in the halftonemode of image reading operation are also stored into the attributememory 212 in the control circuit 170C. Subsequently to the step I12,the central processing unit 172 reverts to the main routine programdescribed with reference to FIG. 22 to check if any other command signalis received from the control panel 140B or the editor module 200B. If itis determined at step I11 that the request for the density for imagereading designated by the signal S_(D1+) or S_(D1-) or the signalS_(D2+) or S_(D2-) received for the selected halftone mode of imagereading operation is not validly acceptable and accordingly the answerfor step I11 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 22 to check if any other command signal is received from thecontrol panel 140B or the editor module 200B.

FIG. 24 shows the details of the area attribute designation controlsubroutine program H04 also included in the main routine programhereinbefore described with reference to FIG. 22. As has been noted, thecentral processing unit 172 is enabled to execute this area attributedesignation control subroutine program H04 when, and only when, theeditor communication grant key 206 on the editor module 200B isdepressed to grant transmission of data and command signals from theeditor module 200 to the central processing unit 172.

The area attribute designation control subroutine program H04 startswith step J01 to determine which command signal is received from theeditor module 200B. The command signal to be detected at this step J01may be the signal produced with any of the image editing key "E",density control key "D", simple binarization density key "SB" andhalftone density key "HT" provided on the editor module 200B. As hasbeen noted, the image editing key "E" is used to enter an instruction toselect the modes of operation designated through the keys "F1" to "F7"in respect of the designated local area of the document D. The densitycontrol key "D" is used to enter an instruction that the image densityfor the specified local area "A1" or "A2" of the document D is to bedesignated from the density "plus" key 216 or from the density "minus"key 218. The simple binarization density key "SB" is used to enter aninstruction that the simple binarization mode of image reading operationis to be selected for the image density designated or to be designatedthrough use of the density "plus" or "minus" key 216 or 218. Likewise,the halftone density key "HT" is used to enter an instruction that thehalftone mode of image reading operation is to be selected for the imagedensity designated or to be designated through use of the density "plus"or "minus" key 216 or 218.

If it is detected at step J01 that there is the command signal receivedfrom the image editing key "E" on the editor module 200B, the centralprocessing unit 172 proceeds to step J02 to check if the request for themodes of operation designated through the keys "F1" to "F7" on theeditor module 200B in respect of the designated local area of thedocument D are validly acceptable in the apparatus and/or the externalprinter unit. If the answer for this step J02 is given in theaffirmative, the central processing unit 172 proceeds to step J03 toselect the modes of operation designated by the keys "F1" to "F7" andsets the lower four bits d₃, d₂, d₁ and d₀ of the attribute signalS_(ATT) to logic "0" and/or logic "1" states for each of all the pixelsin the designated local area of the document D. The bits d₃, d₂, d₁ andd₀ of the attribute signal S_(ATT) thus set to logic "0" and/or logic"1" states and representative of the modes of operation designated bythe keys "F1" to "F7" on the editor module 200B are stored into theattribute memory 212 in the control circuit 170C. The central processingunit 172 then reverts to the main routine program described withreference to FIG. 22 to check if any other command signal is receivedfrom the control panel 140B or from the editor module 200B. If it isdetermined at step J02 that the request for the modes of operationdesignated by the keys "F1" to "F7" are not validly acceptable andaccordingly the answer for this step J02 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 22 to check if any othercommand signal is received from the control panel 140B or from theeditor module 200B.

On the other hand, if it is detected at step J01 that there are thecommand signals received from the density control key "D" and the simplebinarization density key "SB" on the editor module 200B, the centralprocessing unit 172 proceeds to step J04 to check if the request for theimage density for the specified local area of the document D asdesignated from the density "plus" key 216 or from the density "minus"key 218 is validly acceptable in the apparatus and/or the externalprinter unit. If the answer for this step J04 is given in theaffirmative, the central processing unit 172 proceeds to step J05 toselect the image density designated by the density "plus" or "minus" key216 or 218 and sets the intermediate four bits d₇, d₆, d₅ and d₄ of theattribute signal S_(ATT) to logic "0" and/or logic "1" states indicatingthe designated image density for each of all the pixels in thedesignated local area of the document D. The bits d₇, d₆, d₅ and d₄ ofthe attribute signal S_(ATT) thus set to logic "0" and/or logic "1"states and representative of the image density designated by the density"plus" or "minus" key 216 or 218 on the editor module 200B are alsostored into the attribute memory 212 in the control circuit 170C. Thecentral processing unit 172 then reverts to the main routine programdescribed with reference to FIG. 22 to check if any other command signalis received from the control panel 140B or from the editor module 200B.If it is determined at step J04 that the request for the image densitydesignated by the density "plus" or "minus" key 216 or 218 is notvalidly acceptable and accordingly the answer for this step J04 is givenin the negative, the central processing unit 172 immediately reverts tothe main routine program described with reference to FIG. 22 to check ifany other command signal is received from the control panel 140B or fromthe editor module 200B.

Furthermore, if it is detected at step J01 that there are the commandsignals received from the density control key "D" and the halftonedensity key "HT" on the editor module 200B, the central processing unit172 proceeds to step J06 to check if the request for the image densityfor the specified local area of the document D as designated from thedensity "plus" key 216 or from the density "minus" key 218 is validlyacceptable in the apparatus and/or the external printer unit. If theanswer for this step J06 is given in the affirmative, the centralprocessing unit 172 proceeds to step J07 to select the image densitydesignated by the density "plus" or "minus" key 216 or 218 and sets theupper four bits d₁₁, d₁₀, d₉ and d₈ of the attribute signal S_(ATT) tologic "0" and/or logic "1" states indicating the designated imagedensity for each of all the pixels in the designated local area of thedocument D. The bits d₁₁ , d₁₀, d₉ and d₈ of the attribute signalS_(ATT) thus set to logic "0" and/or logic "1" states and representativeof the image density designated by the density "plus" or "minus" key 216or 218 on the editor module 200B are also stored into the attributememory 212 in the control circuit 170C. The central processing unit 172then reverts to the main routine program described with reference toFIG. 22 to check if any other command signal is received from thecontrol panel 140B or from the editor module 200B. If it is determinedat step J06 that the request for the image density designated by thedensity "plus" or "minus" key 216 or 218 is not validly acceptable andaccordingly the answer for this step J06 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 22 to check if any othercommand signal is received from the control panel 140B or from theeditor module 200B.

Fourth Preferred Embodiment (FIGS. 25 to 45)

Description will be hereinafter made in regard to a fourth preferredembodiment of an image reading apparatus according to the presentinvention. The fourth preferred embodiment of the present invention ischaracterized in that the valid density for image reading can beadjusted not only manually through manipulation of keys on the controlpanel but also in an automatic mode manually selected by the operator ofthe apparatus. In the fourth preferred embodiment of the presentinvention is also used the mechanical and optical arrangement describedwith reference to FIG. 1.

FIG. 25 shows an example of the key/indicator configuration of a controlpanel 140C which also forms part of the fourth preferred embodiment ofan image reading apparatus according to the present invention. On thecontrol panel 140C are provided a scan start key 142, a common clear key144, a four-digit eight-segment numerical display section 146, an imagescale-up key 148, an image scale-down key 150, a sheet size indicatorsection 152, a first sheet size select key 154, a second sheet sizeselect key 156, a character mode select key 158, and a halftone modeselect key 160. The functions of these keys and display/indicatorsections on the control panel 140C are similar to those of theirrespective equivalents in the control panel 140A described withreference to FIG. 2 and will not be herein described with reference toFIG. 25.

On the control panel 140C of the fourth preferred embodiment of thepresent invention is further provided a density indicator section 162consisting of a series of subsections arranged in the order of lightnessindicated by numerals "1" to "9". The density indicator section 162 isused to indicate the selected density for image reading manually enteredthrough the control panel 140C. The operator of the apparatus is allowedto manually enter a desired density for image reading manually with useof a manual density "plus" key 164 to enter an instruction to increasethe valid degree of lightness for image reading and a manual density"minus" key 166 to enter an instruction to decrease the valid degree oflightness.

The control panel 140C shown in FIG. 25 further comprises an editorcommunication grant key 206 (labelled "EDIT") used to enter aninstruction to grant reception of data and commands from the editormodule 200A, and an editor information display section 208 for visuallyindicating the data received from the editor module 200A. When theeditor communication grant key 206 is depressed after the key 206 wasonce depressed, the instruction which has been entered to grantreception of data and commands from the editor module 200A is cancelledand entry of data and command signals through the editor module 200A isinvalidated.

The operator of the apparatus is allowed to select an automatic densitycontrol mode through manipulation of an automatic density control key222. In association with this automatic density control key 222 isprovided an automatic density control mode indicator 224 which isactivated to continuously illuminate when the automatic density controlmode is selected with the automatic density control key 222 depressed bythe operator. The automatic density control mode indicator 224 istypically implemented by a semiconductor light emitting diode (LED).

In the fourth preferred embodiment of the present invention, the validdensity for image reading can be adjusted through manipulation of themanual density "plus" key 164 or manual density "minus" key 166 when theautomatic density control mode indicator 224 is turned off. When theautomatic density control key 222 is depressed so that the automaticdensity control mode indicator 224 is turned on and illuminating, thevalid density for image reading is adjusted automatically on the basisof the control data generated by the preliminary scanning of thedocument to be reproduced.

FIG. 26 shows an editor module 200C which forms part of the fourthpreferred embodiment of the present invention. The editor module 200C isessentially similar to its counterpart used in the first preferredembodiment of the present invention and largely consists of a tabletsection 202 and a key section 204. In the key section 204 are providedcontrol keys including a trimming key "F1", a masking key "F2", awhite/black reverse key "F3", a simple binarization mode select key"F4", first and second dither-pattern halftone mode select key "F5" and"F6", and a trim/mask cancel key "F7". These keys "F1" to "F7" are usedfor purposes similar to those of their respective equivalents providedin the editor module 200A used in the first preferred embodiment of thepresent invention. In the key section 204 of the editor module 200Cherein shown are further provided a data-clear key "C" used to enter aninstruction to clear all the data which have been entered to define alocal area within the document on the table section 202, and a data-sendkey "S" used to enter an instruction to transmit to the control circuitof the apparatus the data and instructions entered through the editormodule 200C in respect of the document on the table section 202.

Thus, the fourth preferred embodiment of the present invention also hasseveral kinds of attributes of image reading operation that areachievable by the use of the keys "F1" to "F7". These attributes ofimage reading operation are essentially similar to those which areachievable in each of the second and third preferred embodiments of thepresent invention and include whiting (or blackening) out the imageoutside or inside a specified local area (key "F1" or "F2"), reversingthe white and black features of an image on a document (key "F3"),selecting the simple binarization or halftone mode of image readingoperation (key "F4"), and selecting the first or second prescribeddither pattern for the halftone mode of image reading operation (key"F5" or "F6").

FIG. 27 shows the general construction and arrangement of a controlcircuit 170D for use in the fourth preferred embodiment of an imagereading apparatus according to the present invention. The controlcircuit 170C for use in the fourth preferred embodiment of the presentinvention is essentially similar to the control circuit 170B or 170C ofeach of the second and third preferred embodiments of the presentinvention hereinbefore described. In the control circuit 170D hereinshown, the central processing unit 172 is thus responsive not only tothe command signals supplied from the control panel 140C but to the dataand command signals S_(ED) generated in and supplied from the editormodule 200C hereinbefore described with reference to FIG. 26. As hasbeen noted, the data and command signals S_(ED) generated by any ofthese keys on the editor module 200C are accepted by the centralprocessing unit 172 only when the editor communication grant key 206 isdepressed on the control panel 140C and are invalidated when the key 206is depressed after the key was once depressed.

The command signals which the central processing unit 172 used in thefourth preferred embodiment of the present invention is to receive fromthe control panel 140C include an automatic density control mode selectsignal S_(AUTO) produced when the automatic density control mode isselected with the automatic density control key 222 depressed by theoperator. On receipt of this automatic density control mode selectsignal S_(AUTO), the central processing unit 172 outputs a signaleffective to activate the automatic density control mode indicator 224.

Responsive to the data and command signals S_(ED) supplied from theeditor module 200C and/or to the signal supplied from any of the manualdensity "plus" and "minus" keys 164 and 166 on the control panel 140C,the central processing unit 172 generates an attribute signal S_(ATT)indicative of selected ones of the attributes of image readingoperation. The attribute signal S_(ATT) thus representative of theselected attributes of image reading operation is supplied to and storedinto an attribute memory 212 implemented by a semiconductorrandom-access memory.

The signal S_(ATT) to be generated by the central processing unit 172 isprovided in the form of a sequence of four bits d₃ to d₀ each of logic"1" or "0" state. These four bits d₃ to d₀ of the attribute signalS_(ATT) provide first to fourth fractions, respectively, of the signalS_(ATT) and are similar to their respective equivalents of the attributesignal S_(ATT) used in the control circuit 170B of the second preferredembodiment of the present invention as hereinbefore described withreference to FIG. 15.

Thus, the bit d₃ of the attribute signal S_(ATT) providing the firstfraction of the signal S_(ATT) indicates selection of the blanking outof an image pixel when set to logic "0" state and selection of thenon-blanking of a pixel when set to logic "1" state. The first fractionof the attribute signal S_(ATT) provided by the bit d₃ of the signalS_(ATT) is supplied to one control terminal of the binarizing comparatorcircuit 190.

The bit d₂ of the attribute signal S_(ATT) providing the second fractionof the signal S_(ATT) indicates selection of the non-reversing of thewhite and black features of an image when set to logic "0" state andselection of the reversing of the white and black features of an imagewhen set to logic "1" state. The second fraction of the attribute signalS_(ATT) provided by the bit d₂ of the signal S_(ATT) is supplied to onecontrol terminal of the image signal output circuit 198. To anothercontrol terminal of the image signal output circuit 198 is supplied avalid image area signal S_(VIA) of logic "1" or "0" state from thecentral processing unit 172.

The bit d₁ of the attribute signal S_(ATT) providing the third fractionof the signal S_(ATT) indicates selection of the simple binarizationmode of image reading operation when set to logic "0" state andselection of the halftone mode of image reading operation when set tologic "1" state. The third fraction of the attribute signal S_(ATT)provided by the bit d₁ of the signal S_(ATT) is supplied to the controlterminal of the simple-binarization/halftone mode selector circuit 196.Responsive to this mode select bit d₁, the simple binarization/halftonemode selector circuit 196 supplies either the simple binarizationthreshold signal S_(BT) or the halftone threshold signal S_(HD)depending on the logic state of the bit d₁.

The bit d₀ of the attribute signal S_(ATT) providing the fourth fractionof the signal S_(ATT) indicates selection of the first prescribed ditherpattern simple binarization mode of image reading operation when set tologic "0" state and selection of the the second dither pattern when setto logic "1" state. The fourth fraction of the attribute signal S_(ATT)provided by the bit d₀ of the signal S_(ATT) is supplied to the halftonethreshold generator circuit 194, which is thus enabled to select thefirst or second prescribed dither pattern depending on the logic stateof the bit d₀.

While the bits d₃, d₂ and d₀ of the attribute signal S_(ATT) used in thefourth preferred embodiment of the present invention are to be generatedexclusively responsive to command signal supplied from the editor module200C, the bit d₁ of the attribute signal S_(ATT) may be generated eitherresponsive to a command signal supplied from the editor module 200C orto a command signal supplied from the control panel 200C described withreference to FIG. 25. The central processing unit 172 responsive tocommand signals supplied from the editor module 200C is enabled togenerate the bits d₃ to d₀ of the attribute signal S_(ATT) on conditionthat the editor communication grant key 206 is depressed to granttransmission of data and command signals from the editor module 200 tothe central processing unit 172. Any data and command signals which maybe produced in the editor module will be invalidated when the key 206 isdepressed for a second time.

When the editor communication grant key 206 is depressed so thattransmission of data and command signals from the editor module 200 tothe central processing unit 172, the bit d₃ of the attribute signalS_(ATT) is set to logic "0" state when the trimming key "F1" or themasking key "F2" on the editor module 200C is depressed, and the bit d₂is set to logic "1" state when the white/black reverse key "F3" on theeditor module 200C is depressed. The bit d₁ of the attribute signalS_(ATT) is set to logic "0" state when the simple binarization modeselect key "F4" on the editor module 200C is depressed, and the bit d₀of the attribute signal S_(ATT) is set to logic "0" state when the firstdither-pattern halftone mode select key "F5" on the editor module 200Cis depressed and is set to logic "1" state when the seconddither-pattern halftone mode select key "F6" on the editor module 200Cis depressed.

On the other hand, when the editor communication grant key 206 which hasonce been depressed is depressed for a second time, transmission of dataand command signals from the editor module 200C to the centralprocessing unit 172 is prohibited. In this instance, the centralprocessing unit 172 is qualified to set the bit d₁ of the attributesignal S_(ATT) to logic "0" state when the character mode select key 158on the control panel 140C is depressed and to logic "1" state when thehalftone mode select key 160 on the control panel 140C is depressed. Theremaining bits d₃, d₂ and d₀ of the attribute signal S_(ATT) are set tologic states assigned to standard modes of operation predetermined bydefault rules and could not be varied from the control panel 140C. Ashas been described in regard to the second preferred embodiment of thepresent invention, the standard modes of operation represented by thebits d₃, d₂ and d₀ of such logic states are the non-blanking of a pixelrepresented by the bit d₃ of logic "1" state, the non-reversing of thewhite and black features of an image represented by the bit d₂ of logic"0" state, and the first prescribed dither pattern simple binarizationmode of image reading operation represented by the bit d₀ of logic "0".

In the control circuit 170D of the fourth preferred embodiment of thepresent invention are further provided a simple binarization modedensity data storage memory 226 and a halftone mode density data storagememory 228 each implemented by a random-access memory. Each of thesesimple binarization and halftone mode density data storage memories 226and 228 is responsive to the shaded digital image density data signalsS_(SDD) supplied from the shading circuit 188, the bit d₁ of theattribute signal S_(ATT) supplied from the attribute memory 212, andcontrol signals supplied from the central processing unit 172. Thus,each of the simple binarization and halftone mode density data storagememories 226 and 228 is adapted to store data indicating the originalimage densities represented by the shaded digital image density datasignals S_(SDD). The control signals to be supplied from the centralprocessing unit 172 to each of the density data storage memories 226 and228 include a density data signal generated in the control panel 140C,and a read/write control signal S_(R/W) to select either a read cycle ora write cycle in the memory 226 or 228. The control signals thussupplied from the central processing unit 172 are transmitted through amemory control circuit 230 to the simple binarization mode density datastorage memory 226 or to the halftone mode density data storage memory228 depending on the logic state of the bit d₁ of the attribute signalS_(ATT) supplied from the attribute memory 212. The density datarepresenting the original image density of each image pixel is storedinto the density data storage memory 226 or 228 in response to aread/write control signal S_(R/W) of, for example, logic "0" statepassed through the control circuit 230 or fetched from the memory 226 or228 in response to a read/write control signal S_(R/W) of, for example,logic "1" state passed through the control circuit 230.

As in the control circuit 170B or 170C of the second or third preferredembodiment of the present invention, the image density data in the formof the shaded digital image density data signals S_(SDD) supplied to thebinarizing comparator circuit 190 and representing the originaldensities of the pixels forming the image on the document D is comparedwith the threshold signal S_(BT) supplied from the simple binarizationthreshold generator circuit 192 or with the threshold signal S_(HT)supplied from the halftone threshold signal generator circuit 194through the simple-binarization/halftone mode selector circuit 196. Thebinarizing comparator circuit 190 is thus operative to generate binaryimage signals each of logic "1" or "0" state responsive to the shadeddigital image density data signals S_(SDD).

In the meantime, the data representing the valid density for imagereading is stored in the simple binarization mode density data storagememory 210 or the halftone mode density data storage memory 210. Thisdata has been originally generated either on the basis of the densitystep-up or step-down signal S_(D+) or S_(D-) produced by the manualdensity plus" or "minus" key 164 or 166 on the control panel 140C orautomatically with the automatic density control key 224 depressed onthe control panel 140C. The central processing unit 172 formulates theattribute signal S_(ATT) on the basis of the data thus read from thesimple binarization or halftone mode density data storage memory 226 or228 and loads the signal S_(ATT) into the attribute memory 212. Theattribute memory 212 then distributes the bits the bit d₃ to thebinarizing comparator circuit 190, the bit d₂ to the image signal outputcircuit 198, and the bit d₁ to the simple-binarization/halftone modeselector circuit 196 as has been described.

Responsive to the bits d₃ to d₀ of the attribute signal S_(ATT) thussupplied from the central processing unit 172, the simple binarizationthreshold generator circuit 192 outputs the simple binarizationthreshold signal S_(BT) indicative of a fixed threshold value for use inthe simple binarization mode of image reading operation, or the halftonethreshold generator circuit 194 outputs the halftone threshold signalS_(HT) indicative of a stepwise variable threshold value for use in thehalftone mode of image reading operation. The halftone threshold signalS_(HT) output from the halftone threshold generator circuit 194 isstepwise variable in accordance with the first or second dither patterndepending on the logic state of the bit d₀ of the attribute signalS_(ATT). The simple binarization threshold signal S_(BT) thus outputfrom the simple binarization threshold generator circuit 192 or thehalftone threshold signal S_(HT) output from the halftone thresholdsignal generator circuit 194 is supplied to the binarizing comparatorcircuit 190 through the simple-binarization/halftone mode selectorcircuit 196 depending on the logic state of the mode select bit d₁ whichforms part of the attribute signal S_(ATT) received from the attributememory 212.

Each of these binary image signals generated in the binarizingcomparator circuit 190 responsive to the shaded digital image densitydata signals S_(SDD) is combined with the bit d₃ of the attribute signalS_(ATT) in a logic "AND" operation so that a binary image signal oflogic "1" or "0" state is generated in response to each of the shadeddigital image density data signals S_(SDD). Each of the binary imagesignals thus generated is further combined in a logic "AND" operationwith the simple binarization threshold signal S_(BT) output from thesimple binarization threshold generator circuit 192 or the halftonethreshold signal S_(HT) output from the halftone threshold signalgenerator circuit 194 with the result that a binary image signal S_(OUT)of logic "1" or "0" state is generated in respect of each of the shadeddigital image density data signals S_(SDD). The binarizing comparatorcircuit 190 supplies the output signals S_(OUT) in non-inverted form toone input terminal of the image signal output circuit 198 and ininverted form to the other input terminal of the output circuit 198through the inverter 214.

Responsive to the white/black reversing bit d₂ of the attribute signalS_(ATT), the image signal output circuit 198 elects either thenon-inverted binary image signals S_(OUT) or the inverted versions ofthe signals S_(OUT) depending on the logic state of the white/blackreversing bit d₂. Each of the non-inverted binary image signals S_(OUT)or of the inverted versions of the signals S_(OUT) is combined with thevalid image area signal S_(VIA) of logic "1" or "0" state from thecentral processing unit 172 in a logic "AND" operation. The resultantbinary signals are delivered to a signal processing circuit of anyexternal output unit such as a printer or a display unit (not shown) toreproduce the image represented by the output signals from the signaloutput circuit 198.

FIG. 28 is a flowchart showing a main routine program to be executed bythe central processing unit 172 included in the control circuit 170Dhereinbefore described with reference to FIG. 27.

The execution of the main routine program shown in FIG. 28 is startedwhen the apparatus is initially switched in. The main routine programstarts with step K01 at which the registers included in the centralprocessing unit 172 and the line memory 176 are reset. The step K01 isfollowed by step K02 to check for any command signal supplied from thecontrol panel 140C. The command signal to be checked for at this stepK02 may be the signal S_(CMD) supplied from any of the scan start key142, common clear key 144, image scale-up and scale-down keys 148 and150 and sheet size select keys 154 and 156, or the character mode selectsignal S_(CM) from the character mode select key 158, the halftone modeselect signal S_(HM) from the halftone mode select key 160, the densitystep-up signal S_(D+) or S_(D-) from the manual density "plus" or"minus" key 164 or 166, or the automatic density control mode selectsignal S_(AUTO) from the automatic density control key 222. When theeditor communication grant key 206 is depressed on the control panel140C, it is checked at step K02 if there is a command signal suppliedfrom any of the keys "F1" to "F7" on the editor module 200C. In theabsence detected of any command signal supplied from the control panel140C or the editor module 200C, the central processing unit 172 repeatsthe step K02 until it is found that there is any command signal S_(CMD)received from the control panel 140C.

The central processing unit 172 proceeds to step K03 and executes a modeshift subroutine program if it is detected at step K02 that there is thesignal from the image scale-up or scale-down key 148 or 150, the signalfrom the sheet size select key 154 or 156, the character mode selectsignal S_(CM) from the character mode select key 158, the halftone modeselect signal S_(HM) from the halftone mode select key 160, the densitystep-up or step-down signal S_(D+) or S_(D-) from the manual density"plus" or "minus" key 164 or 166, or the automatic density control modeselect signal S_(AUTO). Responsive to any of these signals supplied fromthe control panel 140C, the central processing unit 172 executes thesteps required by the supplied signal on condition that the mode ofoperation requested by the signal is validly acceptable in theapparatus. The details of this mode shift subroutine program K03 will behereinafter described with reference to FIG. 29.

On the other hand, if it is detected at step K02 that there is a commandsignal .supplied from any of the keys "F1" to "F7" on the editor module200C, the central processing unit 172 proceeds to subroutine program K04and executes an area attribute designation control subroutine program.The central processing unit 172 is enabled to execute this areaattribute designation control subroutine program K04 when, and onlywhen, the editor communication grant key 206 on the control panel 140Cis depressed to grant transmission of data and command signals from theeditor module 200 to the central processing unit 172. The details of thearea attribute designation control subroutine program K04 will behereinafter described with reference to FIG. 30.

If it is detected at step K02 that there is the signal supplied from thescan start key 142 on the control panel 140C, the central processingunit 172 proceeds to subroutine program K05 and executes an image readcontrol subroutine program. The details of this image read controlsubroutine program K05 will be hereinafter described with reference toFIG. 31.

FIG. 29 shows the details of the mode shift subroutine program K03included in the routine program hereinbefore described with reference toFIG. 28.

The mode shift subroutine program K03 starts with step L01 to determinewhich command signal is received from the control panel 140C. Thus, ifit is detected at step L01 that there is the signal received from thesheet size select key 154 or 156, the central processing unit 172proceeds to step L02 to check if the request for the size of printoutput sheets designated by the signal received is validly acceptable inthe apparatus and/or the external printer unit. If the answer for thisstep L02 is given in the affirmative, the central processing unit 172proceeds to step L03 to select the size of print output sheetsdesignated by the signal received and thereafter reverts to the mainroutine program described with reference to FIG. 28 to check if anyother command signal is received from the control panel 140C or from theeditor module 200C. If it is determined at step L02 that the request forthe size of print output sheets designated by the signal received is notvalidly acceptable and accordingly the answer for step L02 is given inthe negative, the central processing unit 172 immediately reverts to themain routine program described with reference to FIG. 28 to check if anyother command signal is received from the control panel 140C or from theeditor module 200C.

If it is detected at step L01 that there is the signal received from theimage scale-up or scale-down key 148 or 150, the central processing unit172 proceeds to step L04 to check if the request for thereduction/magnification ratio designated by the signal received isvalidly acceptable in the apparatus and/or the external printer unit. Ifthe answer for this step L04 is given in the affirmative, the centralprocessing unit 172 proceeds to step L05 to select thereduction/magnification ratio designated by the signal received andthereafter reverts to the main routine program described with reference.to FIG. 28 to check if any other command signal is received from thecontrol panel 140C or from the editor module 200C. If it is determinedat step L04 that the request for the reduction/magnification ratiodesignated by the signal received is not validly acceptable andaccordingly the answer for step L04 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 28 to check if any othercommand signal is received from the control panel 140C or from theeditor module 200C.

If it is detected at step L01 that there is the character mode selectsignal S_(CM) received from the character mode select key 158 or thehalftone mode select signal S_(HM) received from the halftone modeselect key 160, the central processing unit 172 proceeds to step L06 tocheck if the request for the simple binarization or halftone mode ofimage reading operation requested by the signal S_(CM) or S_(HM)received is validly acceptable in the apparatus. If the answer for thisstep L06 is given in the affirmative, the central processing unit 172proceeds to step L07 to select the simple binarization or halftone modeof image reading operation requested by the signal S_(CM) or S_(HM)received and sets the bit d₁ of the attribute signal S_(ATT) to logic"0" state or logic "1" state, respectively, for each of all the pixelsto be reproduced. The bit d₁ thus set to logic "0" or "1" state andrepresentative of the simple binarization or halftone mode of imagereading operation as the selected attribute of the image readingoperation to be performed is stored into the attribute memory 212 in thecontrol circuit 170D. It may be herein noted that each of the bits d₃,d₂ and d₀ of the attribute signal S_(ATT) is set to the logic stateassigned to the predetermined standard since the transmission of dataand command signals from the editor module 200C to the centralprocessing unit 172 is currently prohibited with the editorcommunication grant key 206 depressed after the key 206 was oncedepressed. Subsequently to step L07, the central processing unit 172reverts to the main routine program described with reference to FIG. 28to check if any other command signal is received from the control panel140C or from the editor module 200C.

If it is determined at step L06 that the request for the mode of imagereading operation requested by the character or halftone mode selectsignal S_(CM) or S_(HM) received is not validly acceptable andaccordingly the answer for step L06 is given in the negative, thecentral processing unit 172 immediately reverts to the main routineprogram described with reference to FIG. 28 to check if any othercommand signal is received from the control panel 140C or from theeditor module 200C.

If it is detected at step L01 that there is the density step-up orstep-down signal S_(D+) or S_(D-) received from the manual density"plus" or "minus" key 164 or 166, the central processing unit 172proceeds to step L08 to detect whether or not the automatic densitycontrol signal S_(AUTO) is received from the automatic density controlkey 222 on the control panel 140C. In the presence detected of theautomatic density control signal S_(AUTO), the central processing unit172 further checks at step L09 if flag "FAUTO" is set to logic "1"state. If the answer for this step L09 is given in the negative, thecentral processing unit 172 proceeds to step L10 to set the flag "FAUTO"to logic "1" state and thereafter reverts to the main routine programdescribed with reference to FIG. 28 to check if any other command signalis received from the control panel 140C or from the editor module 200C.The setting of the flag "FAUTO" to logic "1" state establishes theautomatic density control mode in the apparatus.

If it is detected at step L09 that the flag "FAUTO" is not set to logic"1" state and accordingly the answer for the step L09 is given in theaffirmative, the central processing unit 172 proceeds to step L11 toreset the flag "FAUTO" to logic "0" state to clear the automatic densitycontrol mode which has been established in the apparatus. Then, thecentral processing unit 172 proceeds to step L12 to accept the densitystep-up or step-down signal S_(D+) or S_(D-) supplied from the manualdensity "plus" or "minus" key 164 or 166 on the control panel 140C. Thecentral processing unit 172 thereafter reverts to the main routineprogram described with reference to FIG. 28 to check if any othercommand signal is received from the control panel 140C or from theeditor module 200C.

If it is found at step L08 that the automatic density control signalS_(AUTO) is not received from the automatic density control key 222 onthe control panel 140C, the central processing unit 172 proceeds to stepL12 to check if the request for the density for image reading designatedby the signal S_(D+) or S_(D-) received from the manual density "plus"or "minus" key 164 or 166 is validly acceptable. If the answer for thisstep L11 is given in the affirmative, the central processing unit 172proceeds to step L13 to select the density for image reading designatedby the signal S_(D+) or S_(D-) received from the manual density "plus"or "minus" key 164 or 166. Subsequently to the step L13, the centralprocessing unit 172 reverts to the main routine program described withreference to FIG. 28 to check if any other command signal is receivedfrom the control panel 140C or from the editor module 200C. If it isdetermined at step L13 that the request for the density for imagereading designated by the signal S_(D+) or S_(D-) received from themanual density "plus" or "minus" key 164 or 166 is not validlyacceptable and accordingly the answer for step L13 is given in thenegative, the central processing unit 172 immediately reverts to themain routine program described with reference to FIG. 28 to check if anyother command signal is received from the control panel 140C or from theeditor module 200C.

FIG. 30 shows the details of the area attribute designation controlsubroutine program K04 also included in the main routine programhereinbefore described with reference to FIG. 28. The area attributedesignation control subroutine program K04 is executed when there is acommand signal received from the editor module 200C with any of the keys"F1" to "F7" on the editor module 200C depressed in respect of thedesignated local area of the document D. As has been noted, the centralprocessing unit 172 is enabled to execute this area attributedesignation control subroutine program K04 when, and only when, theeditor communication grant key 206 on the editor module 200C isdepressed to grant transmission of data and command signals from theeditor module 200C to the central processing unit 172.

The area attribute designation control subroutine program K04 startswith step M01 at which the central processing unit 172 checks if therequest for the modes of operation designated by the command signalsupplied from any of the keys "F1" to "F7" on the editor module 200C inrespect of the designated local area of the document D is validlyacceptable in the apparatus and/or the external printer unit. If theanswer for this step M01 is given in the affirmative, the centralprocessing unit 172 proceeds to step M02 to select the mode of operationdesignated by any of the keys "F1" to "F7" and sets the four bits d₃,d₂, d₁ and d₀ of the attribute signal S_(ATT) to logic "0" and/or logic"1" states for each of all the pixels in the designated local area ofthe document D. The bits d₃, d₂, d₁ and d₀ of the attribute signalS_(ATT) thus set to logic "0" and/or logic "1" states and representativeof the modes of operation designated by the keys "F1" to "F7" on theeditor module 200C are stored into the attribute memory 212 in thecontrol circuit 170D. The central processing unit 172 then reverts tothe main routine program described with reference to FIG. 28 to check ifany other command signal is received from the control panel 140C or theeditor module 200C.

If it is determined at step M01 that the request for the mode ofoperation designated by the command signal from any of the keys "F1" to"F7" is not validly acceptable and accordingly the answer for this stepM01 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 28 to check if any other command signal is received from thecontrol panel 140C or the editor module 200C.

FIG. 31 shows the details of the image read control subroutine programK05 further included in the main routine program hereinbefore describedwith reference to FIG. 28. As has been noted, the image read controlsubroutine program K05 is to be executed by the central processing unit172 when it is detected at step K02 in the main routine program thatthere is present the signal supplied from the scan start key 142 on thecontrol panel 140C.

The image read control subroutine program K05 starts with step N01 tocheck if the flag "FAUTO" is set to logic "1" state selecting theautomatic density control mode of operation. If the answer for this stepN01 is given in the affirmative, the central processing unit 172executes preliminary scan control subroutine program N02 prior to theexecution of the regular scan control subroutine program N03. If it isfound at step N01 that the flag "FAUTO" is not set to logic "1" state sothat the answer for the step N01 is given in the negative, the centralprocessing unit 172 executes the regular scan control subroutine programN03 without executing the preliminary scan control subroutine programN02 and before executing regular scan control subroutine program N03. Ontermination of the regular scan control subroutine program N03, thecentral processing unit 172 reverts to the main routine programdescribed with reference to FIG. 28 to check if any other command signalis received from the control panel 140C or the editor module 200C.

FIGS. 32A and 32B are flowcharts showing the details of the preliminaryscan control subroutine program N02 included in the image read controlsubroutine program K05 hereinbefore described with reference to FIG. 31.As has been noted, the preliminary scan control subroutine program N02is to be executed by the central processing unit 172 when it is detectedat step N01 of the subroutine program K05 that the flag "FAUTO" is setto logic "1" state prior to execution of the regular scan controlsubroutine program N03 also included in the image read controlsubroutine program K05. During execution the preliminary scan controlsubroutine program N02, the central processing unit 172 suppliesmodified reference voltage signals S_(REF) to the analog-to-digitalconverter 186.

As shown in FIG. 32A, the preliminary scan control subroutine programN02 starts with step P01 at which the central processing unit 172 resetsto logic "0" state the valid image area signal S_(VIA) to be supplied tothe control terminal of the image signal output circuit 198. The validimage area signal S_(VIA) being thus reset to logic "0" state, the imagesignal output circuit 198 is disabled from delivering its output signalsto the external unit such as the printer associated with the apparatusembodying the present invention.

The central processing unit 172 thereafter proceeds to step P02 tosupply the control signal S_(EXP) to the voltage regulator circuit 184for the exposure lamp 106. Responsive to the signal S_(EXP) thusreceived from the central processing unit 172, the voltage regulatorcircuit 184 outputs the lamp control voltage signal V_(EXP) to activatethe exposure lamp 106 to illuminate. The central processing unit 172then proceeds to step P03 to check if each of the lamp/mirror carrier118 and mirror carrier 120 is held in a predetermined home position withrespect to the document support table 102. This decision is made on thesignal S_(POS) supplied from the detecting means provided in associationwith each of the lamp/mirror carrier 118 and mirror carrier 120.

If it is found at this step P03 that the lamp/mirror carrier 118 andmirror carrier 120 are not held in their respective home positions, thecentral processing unit 172 proceeds to step P04 to supply the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step P05 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The loop of the steps P04 and P05 is repeateduntil it is confirmed at step P05 that the lamp/mirror and mirrorcarriers 118 and 120 have reached their respective home positions. Whenit is thus found at step P05 that the carriers 118 and 120 have reachedtheir respective home positions and accordingly the answer for the stepP05 turns affirmative, the central processing unit 172 proceeds to stepP06 to reset the signal S_(MD1) and stop the scanner drive motor 132.

Subsequently to this step P06 or when it is confirmed at step P03 thatthe lamp/mirror and mirror carriers 118 and 120 are held in theirrespective home positions, the central processing unit 172 proceeds tostep P07 to supply the motor actuation signal S_(MD1) for a second timeto the motor driver circuit 178 for the scanner drive motor 132.Responsive to the motor actuation signal S_(MD1) thus received from thecentral processing unit 172, the motor driver circuit 178 actuates thescanner drive motor 132 into operation to move the lamp/mirror andmirror carriers 118 and 120 forwardly from their home positions in thedirections indicated by arrowheads a and b in FIG. 1. The document Dplaced on the document support table 102 is now optically scanned by theexposure lamp 106 and the resultant image-bearing beam of light B isdirected past the reflector mirrors 110, 112 and 114 to the image sensor122.

The step P07 is followed by step P08 at which the central processingunit 172 reads the shading data correcting pattern detected from thelower face of the document scale 104 and stored in the line memory 176.On the basis of the shading data correcting pattern read from the linememory 176, the central processing unit 172 formulates the data inaccordance with which shading signals are to be generated in the shadingcircuit 188. The data thus generated in the central processing unit 172is stored into the line memory 176.

The central processing unit 172 then detects at step P09 whether or notthe lamp/mirror carrier 118 and mirror carrier 120 have reached thepositions effective to scan the leading end of the document D placed onthe document support table 102. The step P09 is repeated until it isconfirmed that the document D on the document support table 102 isscanned at its leading end. When it is thus determined at step P09 thatthe document D on the document support table 102 is scanned at itsleading end and accordingly the answer for the step P09 turnsaffirmative, the central processing unit 172 proceeds to step P10 (FIG.32B) whereby the shaded digital image density data signals S_(SDD)supplied from the shading circuit 188 and representing the originaldensities of the pixels forming the image on the document D are loadedinto the simple binarization mode density data storage memory 226 or thehalftone mode density data storage memory 228. Whether the signalsS_(SDD) are to be loaded into the simple binarization mode density datastorage memory 226 or into the halftone mode density data storage memory228 depends on the logic state of the bit d₁ of the attribute signalS_(ATT) supplied from the attribute memory 212.

The central processing unit 172 then proceeds to step P11 to detectwhether or not the lamp/mirror carrier 118 and mirror carrier 120 havereached the positions effective to scan the trailing end of the documentD on the document support table 102. The step P11 is repeated until itis confirmed that the document D on the document support table 102 hasbeen scanned to its trailing end. Thus, the shaded digital image densitydata signals S_(SDD) are loaded into the simple binarization modedensity data storage memory 226 or into the halftone mode density datastorage memory 228 successively for the individual scanning lines untilall the image on the document or in the designated local area of thedocument are scanned. The detailed aspects of this step P10 will behereinafter described.

When it is thus determined at step P11 that the scanning of the documentD on the document support table 102 is complete and accordingly theanswer for the step P11 turns affirmative, the central processing unit172 proceeds to step P12 to cease the supply of the control signalS_(EXP) to the voltage regulator circuit 184 to de-activate the exposurelamp 106. The step P12 is followed by step P13 at which the centralprocessing unit 172 supplies the motor actuation signal S_(MD1) to themotor driver circuit 178 for the scanner drive motor 132. Responsive tothe motor actuation signal S_(MD1) thus received from the centralprocessing unit 172, the motor driver circuit 178 actuates the scannerdrive motor 132 into operation to move the lamp/mirror and mirrorcarriers 118 and 120 toward their home positions in the directionsindicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step P14 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The step P14 is repeated until it isconfirmed that the lamp/mirror and mirror carriers 118 and 120 havereached their respective home positions. When it is thus found at stepP14 that the carriers 118 and 120 have reached their respective homepositions and accordingly the answer for the step P14 turns affirmative,the central processing unit 172 proceeds to step P15 to reset the signalS_(MD1) and stop the scanner drive motor 132.

Thereupon, the central processing unit 172 proceeds to steps P16 and P17to fetch the data representative of the image densities stored in thesimple binarization mode density data storage memory 226 and thehalftone mode density data storage memory 228 and calculate the optimumthreshold values for the simple binarization and halftone modes of imagereading operation. The values thus calculated on the basis of the imagedensity data fetched from the density data storage memories 226 and 228are transmitted in the forms of the simple binarization image-densitysignal S_(BD) and halftone image-density signal S_(HD) to the simplebinarization threshold generator circuit 192 and halftone thresholdgenerator circuit 194, respectively. The threshold generator circuits192 and 194 are thus enabled to output the simple binarization andhalftone threshold signals S_(BT) and S_(HT) which correspond to thecalculated optimum values for the simple binarization and halftone modesof image reading operation. On termination of the steps P16 and P17, thecentral processing unit 172 reverts to the image read control subroutineprogram K03 described with reference to FIG. 31. The detailed aspects ofthe steps P16 and P17 will be hereinafter described.

FIGS. 33A and 33B are flowchart showing the details of the regular scancontrol subroutine program N03 further included in the image readcontrol subroutine program K05 hereinbefore described with reference toFIG. 31. As has been noted, the regular scan control subroutine programN03 is to be executed by the central processing unit 172 when it isdetected at step N01 of the subroutine program K05 that the flag "FAUTO"is reset to logic "0" state or on termination of the preliminary scancontrol subroutine program N02 included in the image read controlsubroutine program K05.

As shown in FIG. 33A, the regular scan control subroutine program N03starts with step Q01 at which the central processing unit 172 suppliesthe control signal S_(EXP) to the voltage regulator circuit 184 for theexposure lamp 106. Responsive to the signal S_(EXP) thus received fromthe central processing unit 172, the voltage regulator circuit 184outputs the lamp control voltage signal V_(EXP) to activate the exposurelamp 106 to illuminate. The central processing unit 172 then proceeds tostep Q02 to check if each of the lamp/mirror carrier 118 and mirrorcarrier 120 is held in a predetermined home position with respect to thedocument support table 102. This decision is made on the signal S_(POS)supplied from the detecting means provided in association with each ofthe lamp/mirror carrier 118 and mirror carrier 120.

If it is found at this step Q02 that the lamp/mirror carrier 118 andmirror carrier 120 are not held in their respective home positions, thecentral processing unit 172 proceeds to step Q03 to supply the motoractuation signal S_(MD1) to the motor driver circuit 178 for the scannerdrive motor 132. Responsive to the motor actuation signal S_(MD1) thusreceived from the central processing unit 172, the motor driver circuit178 actuates the scanner drive motor 132 into operation to move thelamp/mirror and mirror carriers 118 and 120 toward their home positionsin the directions indicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step Q04 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The loop of the steps Q03 and Q04 is repeateduntil it is confirmed at step Q04 that the lamp/mirror and mirrorcarriers 118 and 120 have reached their respective home positions. Whenit is thus found at step Q04 that the carriers 118 and 120 have reachedtheir respective home positions and accordingly the answer for the stepQ04 turns affirmative, the central processing unit 172 proceeds to stepQ05 to reset the signal S_(MD1) and stop the scanner drive motor 132.

Subsequently to this step Q05 or when it is confirmed at step Q02 thatthe lamp/mirror and mirror carriers 118 and 120 are held in theirrespective home positions, the central processing unit 172 proceeds tostep Q06 to supply the motor actuation signal S_(MD1) for a second timeto the motor driver circuit 178 for the scanner drive motor 132.Responsive to the motor actuation signal S_(MD1) thus received from thecentral processing unit 172, the motor driver circuit 178 actuates thescanner drive motor 132 into operation to move the lamp/mirror andmirror carriers 118 and 120 forwardly from their home positions in thedirections indicated by arrowheads a and b in FIG. 1. The document Dplaced on the document support table 102 is now optically scanned by theexposure lamp 106 and the resultant image-bearing beam of light B isdirected past the reflector mirrors 110, 112 and 114 to the image sensor122.

The step Q06 is followed by step Q07 at which the central processingunit 172 reads the shading data correcting pattern detected from thelower face of the document scale 104 and stored in the line memory 176.On the basis of the shading data correcting pattern read from the linememory 176, the central processing unit 172 formulates the data inaccordance with which shading signals are to be generated in the shadingcircuit 188. The data thus generated in the central processing unit 172is stored into the line memory 176.

The central processing unit 172 then detects at step Q08 whether or notthe lamp/mirror carrier 118 and mirror carrier 120 have reached thepositions effective to scan the leading end of the document D placed onthe document support table 102. The step Q08 is repeated until it isconfirmed that the document D on the document support table 102 isscanned at its leading end. When it is thus determined at step Q08 thatthe document D on the document support table 102 is scanned at itsleading end and accordingly the answer for the step Q08 turnsaffirmative, the central processing unit 172 proceeds to step Q09 (FIG.33B) to generate the valid image area signal S_(VIA). The valid imagearea signal S_(VIA) thus generated by the central processing unit 172 atstep Q09 is supplied to the control terminal of the image signal outputcircuit 198.

The central processing unit 172 then proceeds to step Q10 to instructthe attribute memory 212 to distribute the bits d₃ to d₀ of theattribute signal S_(ATT) to the binarizing comparator circuit 190, imagesignal output circuit 198, mode selector circuit 196, halftone modethreshold generator 194 and memory control circuit 230. The originalimage density data represented by the shaded digital image density datasignals S_(SDD) output from the shading generator circuit 188 are thusprocessed in the comparator circuit 190 on the basis of the bits d₃, d₁and d₀ of the attribute signal S_(ATT) and further in the image signaloutput circuit 198 on the basis of the bit d₂ of the attribute signalS_(ATT). Thus, the image density data representing the image in thedesignated local area of the document to be read in the simplebinarization mode of image reading operation is processed on the basisof the threshold value S_(BT) output from the simple binarizationthreshold generator circuit 192 at step P16 of the preliminary scancontrol subroutine program N02 described with reference to FIG. 32. Onthe other hand, the image density data representing the image in thedesignated local area of the document to be read in the halftone mode ofimage reading operation is processed on the basis of the threshold valueS_(HT) output from the simple binarization threshold generator circuit192 at step P17 of the subroutine program N02. In the presence of theflag "FAUTO" of logic "0" state selecting the manual density controlmode of operation, the data generated on the basis of the step-up orstep-down signal S_(D+) or S_(D-) from the density "plus" or "minus" key164 or 166 on the control panel 140C is used for the processing of theimage density data. The detailed aspects of the step Q10 will behereinafter described.

Subsequently to step Q10, the central processing unit 172 detects atstep Q11 whether or not the lamp/mirror carrier 118 and mirror carrier120 have reached the positions effective to scan the trailing end of thedocument D on the document support table 102. The step Q11 is repeateduntil it is confirmed that the document D on the document support table102 has been scanned to its trailing end. When it is thus determined atstep Q11 that the scanning of the document D on the document supporttable 102 is complete and accordingly the answer for the step Q11 turnsaffirmative, the central processing unit 172 proceeds to step Q12 toreset the valid image area signal S_(VIA) which has been supplied to thecontrol terminal of the image signal output circuit 198.

The central processing unit 172 then proceeds to step Q13 to cease thecentral processing unit 172 supply of the control signal S_(EXP) to thevoltage regulator circuit 184 to de-activate the exposure lamp 106. Thestep Q13 is followed by step Q14 at which the central processing unit172 supplies the motor actuation signal S_(MD1) to the motor drivercircuit 178 for the scanner drive motor 132. Responsive to the motoractuation signal S_(MD1) thus received from the central processing unit172, the motor driver circuit 178 actuates the scanner drive motor 132into operation to move the lamp/mirror and mirror carriers 118 and 120toward their home positions in the directions indicated by arrowheads a'and b' in FIG. 1.

The central processing unit 172 then detects at step Q15 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The step Q15 is repeated until it isconfirmed that the lamp/mirror and mirror carriers 118 and 120 havereached their respective home positions. When it is thus found at stepQ15 that the carriers 118 and 120 have reached their respective homepositions and accordingly the answer for the step Q15 turns affirmative,the central processing unit 172 proceeds to step Q16 to reset the signalS_(MD1) and stop the scanner drive motor 132. Subsequently, the centralprocessing unit 172 reverts to the image read control subroutine programK03 described with reference to FIG. 31.

As has been described with reference to FIG. 32, the original imagedensity data representing the shaded digital image data signals S_(SDD)supplied from the shading circuit 188 is at step P10 of the preliminaryscan control subroutine program N02 loaded into the simple binarizationmode density data storage memory 226 or into the halftone mode densitydata storage memory 228 depending on the logic state of the bit d₁ ofthe attribute signal S_(ATT) supplied from the attribute memory 212.

FIG. 34 shows the basic principles on which the original density levelsof pixels forming a frame of image in a character document having arelatively light background area may be binarized in the simplebinarization mode of image reading operation. It is herein assumed thatthe original density levels of the pixels forming the image frame are tobe binarized with use of a relatively low first threshold value T_(A) toproduce the binarized densities of the pixels. FIG. 35 shows thedistribution of the original density levels shown in FIG. 34 and thusassumed to be loaded into the simple binarization mode density datastorage memory 226 at step P10 of the preliminary scan controlsubroutine program N02.

FIG. 36 shows the basic principles on which the original density levelsof pixels forming a frame of image in a character document having arelatively dark background area may be binarized in the simplebinarization mode of image reading operation. In this instance, theoriginal density levels of the pixels forming the image frame areassumed to be binarized with use of a relatively high second thresholdvalue T_(B) to produce the binarized densities of the pixels. FIG. 37shows the distribution of the density levels shown in FIG. 36 and alsoassumed to be loaded into the simple binarization mode density datastorage memory 226 at step P10 of the preliminary scan controlsubroutine program N02.

As will be seen from comparison between the curves indicated in FIGS. 35and 37, the image densities represented by the original image densitydata loaded into the simple binarization mode density data storagememory 226 at step P10 of the subroutine program N02 occur at low levelsmore frequently for the character document having the relatively lightbackground area than for the character document having the relativelydark background area.

On the other hand, FIG. 38 shows the basic principles on which theoriginal density levels of pixels forming a frame of image in aphotographic document having a relatively light background area may bebinarized in the halftone mode of image reading operation. It is hereinassumed that the original density levels of the pixels forming the imageframe are to be binarized with use of a relatively low first set ofthreshold values T_(GA) to produce the binarized densities of thepixels. FIG. 39 shows the distribution of the original density levelsshown in FIG. 38 and also assumed to be loaded into the simplebinarization mode density data storage memory 226 at step P10 of thepreliminary scan control subroutine program N02.

FIG. 40 shows the basic principles on which the original density levelsof pixels forming a frame of image in a photographic document having arelatively dark background area may be binarized in the halftone mode ofoperation. It is herein assumed that the original density levels of thepixels forming the image frame are to be binarized with use of arelatively high second set of threshold values T_(GB) to produce thebinarized densities of the pixels. FIG. 41 shows the distribution of theoriginal density levels shown in FIG. 40 and assumed to be loaded intothe simple binarization mode density data storage memory 226 at step P10of the preliminary scan control subroutine program N02.

Comparison between the curves indicated in FIGS. 39 and 41 will revealthat the image densities represented by the original image density dataloaded into the halftone mode density data storage memory 228 at stepP10 of the preliminary scan control subroutine program N02 also occur atlow levels more frequently for the photographic document having therelatively light background area than for the photographic documenthaving the relatively dark background area.

On the basis of the original image density data loaded into the simplebinarization mode density data storage memory 226 at step P10 of thepreliminary scan control subroutine program N02, the optimum thresholdvalue for use in the simple binarization mode of image reading operationis determined at step P16 of the subroutine program N02. In thisinstance, such an optimum threshold value for the simple binarization isto be fixed in the vicinity of the relatively low first threshold valueT_(A) for the character document having the relatively light backgroundarea, as will be seen from FIG. 35. For the character document havingthe relatively dark background area, the optimum threshold value for thesimple binarization is to be fixed in the vicinity of the relativelyhigh second threshold value T_(B) for the character document having therelatively dark background area, as will be seen from FIG. 37.

Furthermore, the optimum threshold value for use in the halftone mode ofimage reading operation is determined at step P17 of the preliminaryscan control subroutine program N02 on the basis of the original imagedensity data loaded into the halftone mode density data storage memory228 at step P10 of the subroutine program N02. In this instance, theoptimum threshold value for the halftone mode of image reading operationis to be fixed within the range of the relatively low first set ofthreshold values T_(GA) for the photographic document having therelatively light background area, as will be seen from FIG. 39. For thephotographic document having the relatively dark background area, theoptimum threshold value for the halftone mode of image reading operationis to be fixed within the range of the relatively high second set ofthreshold values T_(GB) for the photographic document having therelatively light background area, as will be seen from FIG. 39.

FIG. 42 shows the input-output characteristics of a group of conceptualthreshold values, viz., the relationship between the original imagedensities indicated by the shaded image density signals S_(SDD) and theimage densities binarized on the principles indicated in FIG. 38. FIG.43 shows an example of the dither pattern which may be used to providethe input-output characteristics indicated in FIG. 42. As will be seenfrom FIGS. 42 and 43, a group of conceptual threshold values rangesbetween 15(H) and 9C(H) for a photographic document having a relativelylight background area.

FIG. 44 shows the relationship between the original image densitiesindicated by the shaded image density signals S_(SDD) and the imagedensities binarized on the principles indicated in FIG. 40. FIG. 45shows an example of the dither pattern which may be used to provide theinput-output characteristics indicated in FIG. 44. From FIGS. 44 and 45will be seen that a group of conceptual threshold values ranges between69(H) and FF(H) for a photographic document having a relatively darkbackground area.

Fifth Preferred Embodiment (FIG. 46 to 56)

Description will be hereinafter made in regard to a fifth preferredembodiment of an image reading apparatus according to the presentinvention. In the fifth preferred embodiment of the present inventionare used the control panel 140C shown in FIG. 25 and editor module 200Cshown in FIG. 26 in addition to the mechanical and optical arrangementdescribed with reference to FIG. 1. The fifth preferred embodiment ofthe present invention is characterized by the provision of a referencevoltage generator connected between the central processing unit 172 andthe analog-to-digital converter 186.

FIG. 46 shows the general construction and arrangement of a controlcircuit 170E for use in the third preferred embodiment of an imagereading apparatus according to the present invention. The controlcircuit 170E for use in the fifth preferred embodiment of the presentinvention is essentially similar to the control circuit 170D of thefifth preferred embodiment of the present invention. In the controlcircuit 170E herein shown, however, there is additionally provided areference voltage generator circuit 232 having parallel input terminalsconnected to the central processing unit 172 and parallel outputterminals connected to the control terminals of the analog-to-digitalconverter 186. The reference voltage generator circuit 232 further has acontrol terminal responsive to the bit d₁ of the four-bit attributesignal S_(ATT).

As has been described, the bit d₁ of the attribute signal S_(ATT) isindicative of the selection of the simple binarization mode of imagereading operation when set to logic "0" state and the selection of thehalftone mode of image reading operation when set to logic "1" state.The fraction of the attribute signal S_(ATT) thus provided by the bit d₁of the signal S_(ATT) is supplied to not only to the control terminal ofthe reference voltage generator circuit 232 but to the control terminalof the simple-binarization/halftone mode selector circuit 196 and thecontrol terminal of the memory control circuit 230 for the simplebinarization and halftone mode density data storage memories 226 and228.

As has been described, the analog-to-digital converter 186 receivesanalog image density data signal signals S_(DV) representative of theimage information contained in a beam of light incident on the imagesensor 128. As illustrated in FIG. 47, the image sensor 128 comprises anarray 234 of semiconductor charge-coupled devices (CCDs) which has acontrol terminal connected to the clock generator circuit 174. The CCDarray 234 thus forming part of the image sensor 128 is thus responsiveto the sample-and-hold signals S_(SH) supplied from the clock generatorcircuit 174 to output analog signals respectively representative of theimage densities of the pixels of each line of pixel elements on thedocument scanned by the image sensor 128. The analog image density datasignals out from the individual elements of the CCD array 234 aresampled by a sample-and-hold circuit 236 also responsive to thesample-and-hold signals S_(SH) and, upon amplification by an amplifier238, output as the analog image density data signals S_(DV) from theimage sensor 128 to the analog-to-digital converter 186 as shown in FIG.47 and further in FIG. 48.

The voltage of the analog image density data signal S_(DV) out from eachof the individual elements of the CCD array 234 is typically variablewithin the range of 0 volts to 2.5 volts, decreasing toward 0 volts asthe image detected becomes lighter and increasing toward 2.5 volts asthe image detected becomes darker, as will be seen from FIG. 49.Responsive to such an analog image density data signal S_(DV) andfurther to the reference voltage signals S_(REF) supplied from thereference voltage generator circuit 232, the analog-to-digital converter186 converts the input signal S_(VD) into corresponding digital signalsS_(DD) which stepwise vary between, for example, zero volts and 2.5volts as indicated in FIG. 50.

As has been described, the digital signals S_(DD) thus output from theanalog-to-digital converter 186 are supplied to the shading circuit 188which compensates for the spurious components in the supplied signalsS_(DD). The image density data provided in the form of shaded digitalimage density data signals S_(SDD) output from the shading circuit 188to the binarizing comparator circuit 190 is supplied on one hand to thebinarizing comparator circuit 190 and on the other hand to the linememory 176.

As shown in FIG. 48, the reference voltage generator circuit 232connected between the central processing unit 172 and analog-to-digitalconverter 186 is responsive to the bit b₁ of the attribute signalS_(ATT) and further to a reference voltage control signal S_(RC) outputfrom the central processing unit 172. The image sensor 128 is responsiveto sample-and-hold signals S_(SH) supplied from the clock generatorcircuit 174 and outputs analog image density data signals S_(DV)representative of the image information contained in a beam of lightincident on the sensor 128. The analog-to-digital converter 186 receivesthese analog image density data signals S_(DV) from the array of thecharge-coupled devices forming the image sensor 128 and outputscorresponding digital signals S_(DD) on the basis of the referencevoltage signals S_(REF) supplied from the central processing unit 172.The digital signals S_(DD) thus output from the analog-to-digitalconverter 186 are supplied to the shading circuit 188 which compensatesfor the spurious components in the supplied signals S_(DD) to eliminatethe irregularities in the quantities of light incident on the individualcharge-coupled devices forming the image sensor 128 and theirregularities in the degrees of sensitiveness of the charge-coupleddevices.

The shaded digital image density data signals S_(SDD) thus output fromthe shading generator circuit 188 are representative of the originalpixel densities of the frame of image detected from the document Dcurrently in use. The image density data in the form of the shadeddigital image density data signals S_(SDD) is on one hand stored in theline memory 176 and on the other hand supplied to a binarizingcomparator circuit 190.

On the other hand, the bit d₁ of the attribute signal S_(ATT) is set tologic "0" state when the character mode select key 158 on the controlpanel 140C is depressed and to logic "1" state when the halftone modeselect key 160 on the control panel 140C is depressed. Responsive to thebit d₁ of the attribute signal S_(ATT) set to logic "0" state, thereference voltage generator circuit 232 supplies to theanalog-to-digital converter 186 the reference voltage signals S_(REF)which are formulated to be optimum for the simple binarization mode ofimage reading operation by the reference voltage control signal S_(RC)output from the central processing unit 172. On the other hand, when thebit d₁ of the attribute signal S_(ATT) set to logic "1" state isreceived, the reference voltage generator circuit 232 supplies to theanalog-to-digital converter 186 the reference voltage signals S_(REF)formulated to be optimum for the halftone mode of image readingoperation by the reference voltage control signal S_(RC) from thecentral processing unit 172.

FIG. 51 shows examples of the signals involved in the operation of theanalog-to-digital converter 186. In FIG. 51 is shown an example of theanalog image density data signals S_(DV) which may be supplied from theimage sensor 128 to the analog-to-digital converter 186. FIG. 51 alsoshow examples of the reference voltage signals S_(REF) which may beoutput from the reference voltage generator circuit 232 responsive tothe reference voltage control signal S_(RC) output from the centralprocessing unit 172. In FIG. 51, the plot indicated by full linerepresents examples of the standard reference voltage signals S_(REF)(S)for use in the preliminary scanning of a document and the plotsindicated by dot-and-dash and dots-and-dash lines represent examples ofthe reference voltage signals S_(REF)(D) and S_(REF)(L) to reproducerelatively dark and light images from documents having relatively lightand dark image patterns, respectively, by regular scanning of thedocuments. The standard reference voltage signals S_(REF)(S) for use inthe preliminary scanning operation is variable within the range of 0volts and 2.5 volts which correspond to the image density levels of00(H) and FF(H), respectively. FIG. 51 also shows examples of thedigital image density data signals S_(DD) which may be output from theanalog-to-digital converter 186 responsive to the analog image densitydata signals S_(DV) and the reference voltage signals S_(REF)(S),S_(REF)(D) and S_(REF)(L). In FIG. 51, the waveform indicated by fulllines represents an example of the digital image density data signalsS_(DD)(S) output from the analog-to-digital converter 186 responsive tothe standard reference voltage signals S_(REF)(S) during preliminaryscanning of a document. The waveforms indicated by dot-and-dash anddots-and-dash lines in FIG. 51 represent examples of the digital imagedensity data signals S_(DD)(D) and S_(DD)(L) output from theanalog-to-digital converter 186 responsive to the reference voltagesignals S_(REF)(D) and S_(REF)(L) during regular scanning of documentshaving relatively dark and light image patterns, respectively.

FIGS. 52A and 52B are flowcharts showing the details of the preliminaryscan control subroutine program to be executed by the central processingunit 172 hereinbefore described with reference to FIG. 46. Thepreliminary scan control subroutine program is similar to its equivalentdescribed with reference to FIGS. 32A and 32B and is to be executed bythe central processing unit 172 when it is detected at step N01 of thesubroutine program K05 that the flag "FAUTO" is set to logic "1" stateprior to execution of the regular scan control subroutine program.During execution the preliminary scan control subroutine program, thecentral processing unit 172 supplies the standard reference voltagesignals S_(REF)(S) to the analog-to-digital converter 186.

The preliminary scan control subroutine program to be executed by thecentral processing unit 172 of the fifth preferred embodiment of thepresent invention consists of steps R01 to R17, of which the steps R01to R15 are similar to the steps P01 to P15 of the subroutine program N02described with reference to FIGS. 32A and 32B.

When it is thus found at step R14 that the lamp/mirror and mirrorcarriers 118 and 120 have reached their respective home positions, thecentral processing unit 172 proceeds to step R15 to reset the signalS_(MD1) and stop the scanner drive motor 132. Thereupon, the centralprocessing unit 172 proceeds to steps R16 and R17 to fetch the imagedensity data stored at step R10 in the simple binarization mode densitydata storage memory 226 and the halftone mode density data storagememory 228. At steps R16 and R17, the central processing unit 172further calculates the value for the reference control signal S_(RC) toenable the reference voltage generator circuit 232 to generate theoptimum reference voltage signal for the regular scanning of thepreliminarily scanned document. Responsive to the reference controlsignal S_(RC) thus generated by the central processing unit 172, thereference voltage generator circuit 232 produces the optimum referencevoltage signal S_(REF)(D) or S_(REF)(L) for the regular scanning of thepreliminarily scanned document in respect of the simple binarization orhalftone mode of image reading operation depending on the logic state ofthe bit d₁ of the attribute signal S_(ATT) supplied to the controlterminal of the circuit 232.

FIGS. 53A to 53E show the basic principles on which the binarized imagedensity data signals S_(OUT) are to be produced from the analog imagedensity data signals S_(DV) with the standard reference voltage signalsS_(REF)(S) applied to the analog-to-digital converter 186 during simplebinarization mode of image reading operation. FIGS. 53A, 53B and 53C arediagrams similar to FIG. 51 and thus show an example of the analog imagedensity data signals S_(DV) (FIG. 53A) which may be supplied from theimage sensor 128 to the analog-to-digital converter 186, examples of thereference voltage signals S_(REF) (FIG. 53B) which may be output fromthe reference voltage generator circuit 232, and examples of the digitalimage density data signals S_(DD) (FIG. 53C) which may be output fromthe analog-to-digital converter 186 responsive to the analog imagedensity data signals S_(DV) and the reference voltage signals S_(REF).Furthermore, FIGS. 53C, 53D and 53E are diagrams similar to FIGS. 34 or36, and thus show the basic principles on which the digital imagedensity data signals S_(DD) (FIG. 53C) may be binarized in the simplebinarization mode of image reading operation with use of the thresholdvalue T_(SB) (FIG. 53D) to produce the binarized image density signalsS_(OUT) (FIG. 53E).

The plot indicated in FIG. 53A is obtained with a document having arelatively light image and accordingly the analog image density datasignals S_(DV) supplied from the image sensor 128 to theanalog-to-digital converter 186 has relatively low voltage levels. Ifthe standard reference voltage signals S_(REF)(S) having the minimum andmaximum voltages of 0 volts and 2.5 volts corresponding to the imagedensity levels of 00(H) and FF(H), respectively, are used for theregular scanning of such a document, the digital image density datasignals S_(DD)(S) output from the analog-to-digital converter 186 alsohave relatively low voltage levels as will be seen from FIG. 53C. InFIG. 53C, the maximum voltage level V_(max)(S) of the digital outputsignals S_(DD)(S) from the analog-to-digital converter 186 is shownapproximating the level for an image density level intermediate betweenthe levels 80(H) and FF(H). The result will be that the image reproducedfrom the image density signals S_(OUT) (FIG. 53E) binarized from suchdigital output signals S_(DD)(S) from the analog-to-digital converter186 appear more whitish than the original image on the document does.

In order to make the reproduced image more blackish, it is necessary toproduce the digital output signals from the analog-to-digital converter186 in such a manner that the maximum voltage level of the digitaloutput signals from the analog-to-digital converter 186 is locatedcloser to the maximum density level FF(H) as indicated by phantom linesin FIG. 53C. Such digital image density data signals can be produced bythe use of modified reference voltage signals S_(REF)(D) having a lowermaximum voltage of, for example, 1.875 volt in response to the maximumimage density level FF(H) as indicated by full line in FIG. 54. FIG. 54shows diagrams similar to FIGS. 53A to 53E, respectively, and show thebasic principles on which the binarized image density data signalsS_(OUT) are to be produced from the analog image density data signalsS_(DV) with the modified reference voltage signals S_(REF)(D) applied tothe analog-to-digital converter 186 during simple binarization mode ofimage reading operation.

Modifying the reference voltage characteristics in the above describedmanner is, briefly, to vary the gradient of the characteristic curveabout the origin of the coordinate system or, in other words, as simplyto vary the upper limit value of the reference voltage signals. A changein the upper limit value of the reference voltage signals would resultin changes in the differences between the individual digital outputsignals from the analog-to-digital converter 186 as will be seen fromcomparison between FIGS. 53C and 54. Changes in the differences betweenthe output signals from the analog-to-digital converter 186 in turn willresult in changes in the contrasts of the individual elements of theimage reproduced from the resultant binary image density data signalsS_(OUT) as will be seen from comparison between FIGS. 53D and 54. Suchvariation in the contrasts of the individual elements of the imagereproduced can be compensated for if a suitable bias voltage is added tothe modified reference voltage to increase or decrease the lower limitvalue of the reference signal to be put to actual use.

FIG. 55 shows diagrams similar to FIGS. 53A to 53E, respectively, andshow the basic principles on which the binarized image density datasignals S_(OUT) are to be produced from the analog image density datasignals S_(DV) with the standard reference voltage signals S_(REF)(S)applied to the analog-to-digital converter 186 during halftone mode ofimage reading operation. Thus, the digital image density data signalsS_(DD) may be binarized in the halftone mode of image reading operationwith use of the threshold value T_(HT) to produce the binarized imagedensity signals S_(OUT).

The plot indicated in FIG. 55 is obtained with a document having arelatively dark image and accordingly the analog image density datasignals S_(DV) supplied from the image sensor 128 to theanalog-to-digital converter 186 has relatively high voltage levels. Ifthe standard reference voltage signals S_(REF)(S) having the minimum andmaximum voltages of 0 volts and 2.5 volts corresponding to the imagedensity levels of 00(H) and FF(H), respectively, are used for theregular scanning of such a document, the digital image density datasignals S_(DD)(S) output from the analog-to-digital converter 186 alsohave relatively high voltage levels as will be seen from FIG. 55. Theresult will be that the image reproduced from the image density signalsS_(OUT) binarized from such digital output signals S_(DD)(S) from theanalog-to-digital converter 186 appear more blackish than the originalimage on the document does.

In order to make the reproduced image more whitish, it is necessary toproduce the digital output signals from the analog-to-digital converter186 in such a manner that the intermediate voltage level or weightedmean voltage level of the digital output signals from theanalog-to-digital converter 186 is located close to, for example, thedensity level 80(H) as indicated by a phantom line in FIG. 55. Suchdigital image density data signals can be produced by the use ofmodified reference voltage signals S_(REF)(L) having the maximum voltageof 2.5 volts in response to an image density level approximating thedensity level 80(H) as indicated by full line in FIG. 56. FIG. 56 showsdiagrams similar to FIG. 54 and shows the basic principles on which thebinarized image density data signals S_(OUT) are to be produced from theanalog image density data signals S_(DV) with the modified referencevoltage signals S_(REF)(L) applied to the analog-to-digital converter186 during halftone mode of image reading operation.

Sixth Preferred Embodiment (FIG. 57 to 65)

Description will be hereinafter made in regard to a sixth preferredembodiment of an image reading apparatus according to the presentinvention. The sixth preferred embodiment of the present invention ischaracterized in that the valid density for image reading can beadjusted either automatically or manually in respect of each of thelocal areas which may be designated by the operator of the apparatus. Inthe sixth preferred embodiment of the present invention is also used themechanical and optical arrangement described with reference to FIG. 1.

FIG. 57 shows an example of the key/indicator configuration of a controlpanel 140D which also forms part of the sixth preferred embodiment of animage reading apparatus according to the present invention. On thecontrol panel 140D are provided a scan start key 142, a common clear key144, a four-digit eight-segment numerical display section 146, an imagescale-up key 148, an image scale-down key 150, a sheet size indicatorsection 152, a first sheet size select key 154, and a second sheet sizeselect key 156. The functions of these keys and display/indicatorsections on the control panel 140D are similar to those of theirrespective equivalents in the control panel 140C described withreference to FIG. 25.

On the control panel 140D of the sixth preferred embodiment of thepresent invention is also provided a density indicator section 162consisting of a series of subsections arranged in the order of lightnessindicated by numerals "1" to "9". The density indicator section 162 isused to indicate the selected density for image reading manually enteredthrough the control panel 140D. The operator of the apparatus is allowedto manually enter a desired density for image reading manually with useof a manual density "plus" key 164 to enter an instruction to increasethe valid degree of lightness for image reading and a manual density"minus" key 166 to enter an instruction to decrease the valid degree oflightness.

The control panel 140D shown in FIG. 57 further comprises an editorcommunication grant key 206 used to enter an instruction to grantreception of data and commands from the editor module to be described,and an editor information display section 208 for visually indicatingthe data received from the editor module. When the editor communicationgrant key 206 is depressed after the key 206 was once depressed, theinstruction which has been entered to grant reception of data andcommands from the editor module is cancelled and entry of data andcommand signals through the editor module is invalidated as has beendescribed. The operator of the apparatus is allowed to select anautomatic density control mode through manipulation of an automaticdensity control key 222.

FIG. 58 shows an editor module 200D for use in the sixth preferredembodiment of the present invention. Similarly to its counterpart (FIG.26) in the fourth preferred embodiment of the present invention, theeditor module 200D herein shown largely consists of a tablet section 202and a key section 204 comprising a total of nine control keys. As hasbeen noted with reference to FIG. 26, a square-shaped rectangular areaof a document D such as the area "A1" or the area "A2" herein indicatedby phantom lines can be defined simply by specifying the locations ofthe opposite ends of one of the diagonals of the area "A1" or the area"A2" with use of a light pen.

The control keys provided in the key section 204 of the editor module200D include a trimming key "F1", a masking key "F2", a white/blackreverse key "F3", a simple binarization mode select key "F4", a firstdither-pattern halftone mode select key "F5", a second dither-patternhalftone mode select key "F6", and a trim/mask cancel key "F7". Thefunctions achievable through use of these keys "F1" to "F7" are similarto those of their respective equivalents provided in the editor module200D described with reference to FIG. 26. In the key section 204 of theeditor module 200D are further provided a data-clear key "C" and adata-send key "S", which are also similar to their respectiveequivalents provided in the editor module 200C shown in FIG. 26.

In the key section 204 of the editor module 200D used in the sixthpreferred embodiment of the present invention are provided additionalcontrol keys which include a density "plus" key 216, and a density"minus" key 218. The density "plus" and "minus" keys 216 and 218 arerespectively provided to permit entry of instructions from the editormodule 200D to increase and decrease the valid degree of lightness forimage reading in respect of the specified local area "A1" or "A2" of thedocument D. In association with these density "plus" and "minus" keys216 and 218 is provided a density indicator section 220 consisting of aseries of subsections arranged in the order of lightness indicated bynumerals "1"to "9". The subsection indicating the selected density forimage reading is to be highlighted with the highlight stepwise moved inone direction along the indicator section 220 each time the density"plus" key 216 is depressed or in the opposite direction along theindicator section 220 each time the density "minus" key 218 is depressedby the operator.

In the editor module 200D used in the sixth preferred embodiment of thepresent invention is further provided an automatic density control key240 to allow the operator of the apparatus to select an automaticdensity control mode. In the sixth preferred embodiment of the presentinvention, the valid density for image reading can be adjusted throughmanipulation of the manual density "plus" key 164 or manual density"minus" key 166 for each of the designated local areas "A1" and "A2"when the automatic density control key 222 is depressed after the key222 was once depressed. When the automatic density control key 222 isdepressed for a first time, the valid density for image reading isadjusted automatically for each of the designated local areas "A1" and"A2" on the basis of the control data generated by the preliminaryscanning of the document to be reproduced.

The sixth preferred embodiment of the present invention also has severalkinds of attributes of image reading operation that are achievable bythe use of the keys "F1" to "F7". These attributes of image readingoperation are essentially similar to those which are achievable in thefifth preferred embodiment of the present invention and include whiting(or blackening) out the image outside or inside a specified local area(key "F1" or "F2") , reversing the white and black features of an imageon a document (key "F3"), selecting the simple binarization or halftonemode of image reading operation (key "F4"), and selecting the first orsecond prescribed dither pattern for the halftone mode of image readingoperation (key "F5" or "F6").

FIG. 59 shows the general construction and arrangement of a controlcircuit 170F for use in the fourth preferred embodiment of an imagereading apparatus according to the present invention. The controlcircuit 170F for use in the sixth preferred embodiment of the presentinvention is essentially similar to the control circuit of each of thepreferred embodiments of the present invention hereinbefore described.In the control circuit 170F herein shown, the central processing unit172 is thus responsive not only to the command signals supplied from thecontrol panel 140C but to the data and command signals S_(ED) generatedin and supplied from the editor module 200C hereinbefore described withreference to FIG. 26. As has been noted, the data and command signalsS_(ED) generated by any of these keys on the editor module 200D areaccepted by the central processing unit 172 only when the editorcommunication grant key 206 is depressed on the control panel 140D andare invalidated when the key 206 is depressed after the key was oncedepressed.

The command signals which the central processing unit 172 used in thesixth preferred embodiment of the present invention is to receive fromthe control panel 140D include an automatic density control mode selectsignal S_(AUTO) produced when the automatic density control mode isselected with the automatic density control key 222 depressed by theoperator. On receipt of this automatic density control mode selectsignal S_(AUTO), the central processing unit 172 outputs a signaleffective to activate the automatic density control mode indicator 224.

Responsive to the data and command signals S_(ED) supplied from theeditor module 200D and/or to the signal supplied from any of the manualdensity "plus" and "minus" keys 164 and 166 on the control panel 140C,the central processing unit 172 generates an attribute signal S_(ATT)indicative of selected ones of the attributes of image readingoperation. The attribute signal S_(ATT) thus representative of theselected attributes of image reading operation is supplied to and storedinto an attribute memory 212 implemented by a semiconductorrandom-access memory.

The signal S_(ATT) to be generated by the central processing unit 172 isprovided in the form of two bits d₁ and d₀ each of logic "1" or "0"state. These four bits d₁ and d₀ of the attribute signal S_(ATT) providefirst and second fractions, respectively, of the signal S_(ATT). Thus,the bit d₁ of the attribute signal S_(ATT) providing the first fractionof the signal S_(ATT) indicates selection of the automatic densitycontrol mode when set to logic "0" state and selection of the manualdensity control mode when set to logic "1" state. The first fraction ofthe attribute signal S_(ATT) provided by the bit d₁ of the signalS_(ATT) is supplied from the attribute memory 212 to the centralprocessing unit 172.

The bit d₀ of the attribute signal S_(ATT) providing the second fractionof the signal S_(ATT) indicates selection of the blanking out of animage pixel when set to logic "0" state and selection of thenon-blanking of a pixel when set to logic "1" state. The second fractionof the attribute signal S_(ATT) provided by the bit d₀ of the signalS_(ATT) is supplied to one control terminal of the binarizing comparatorcircuit 190. To another control terminal of the comparator circuit 190is supplied a simple binarization threshold signal S_(BT) generated bythe central processing unit 172 and indicative of the threshold value tobe used for the binarization of the digital image density data signalS_(SDD) supplied from the shading circuit 188. It may be noted that thecomparator circuit 190 is connected directly to the image signal outputcircuit 198 which has a control terminal responsive to a valid imagearea signal S_(VIA) of logic "1" or "0" state from the centralprocessing unit 172.

In the control circuit of the sixth preferred embodiment of the presentinvention, the image density data in the form of the shaded digitalimage density data signals S_(SDD) supplied to the binarizing comparatorcircuit 190 and representing the original densities of the pixelsforming the image on the document D is compared with the simplebinarization threshold signal S_(BT) supplied from the centralprocessing unit 172. The binarizing comparator circuit 190 is thusoperative to generate binary image signals each of logic "1"or "0" stateresponsive to the shaded digital image density data signals S_(SDD).

In the meantime, data representing the valid density for image readingis generated either on the basis of the density step-up or step-downsignal S_(D+) or S_(D-) produced by the manual density "plus" or "minus"key 164 or 166 on the control panel 140D or automatically with theautomatic density control key 224 depressed on the control panel 140D.The central processing unit 172 formulates the attribute signal S_(ATT)on the basis of the data thus generated and loads the signal S_(ATT)into the attribute memory 212. The attribute memory 212 then distributesthe bit d₀ to the binarizing comparator circuit 190 and the bit d₁ backto the central processing unit 172.

Responsive to the bits d₁ of the attribute signal S_(ATT) thus suppliedfrom the attribute memory 212, the binarizing comparator circuit 190combines each of the binary image signals generated therein with the bitd₁ of the attribute signal S_(ATT) in a logic "AND" operation so that abinary image density data signal of logic "1" or "0" state is generatedin response to each of the shaded digital image density data signalsS_(SDD). Each of the binary image signals thus generated is furthercombined in a logic "AND" operation with the threshold signal S_(T)supplied from the central processing unit 172 with the result that abinary image signal S_(OUT) of logic "1" or "0" state is generated inrespect of each of the shaded digital image density data signalsS_(SDD). The binarizing comparator circuit 190 supplies the outputsignals S_(OUT) to the image signal output circuit 198 and via thecircuit 198 to a signal processing circuit of any external output unitsuch as a printer or a display unit (not shown) to reproduce the imagerepresented by the output signals from the signal output circuit 198.

FIG. 60 is a flowchart showing a main routine program to be executed bythe central processing unit 172 included in the control circuit 170Fhereinbefore described with reference to FIG. 59.

The execution of the main routine program shown in FIG. 60 is startedwhen the apparatus is initially switched in. The main routine programstarts with step S01 at which the registers included in the centralprocessing unit 172 and the line memory 176 are reset. The step S01 isfollowed by step S02 to check for any command signal supplied from thecontrol panel 140D. The command signal to be checked for at this stepS02 may be the signal S_(CMD) supplied from any of the scan start key142, common clear key 144, image scale-up and scale-down keys 148 and150 and sheet size select keys 154 and 156, or the density step-upsignal S_(D+) or S_(D-) from the manual density "plus" or "minus" key164 or 166, or the automatic density control mode select signal S_(AUTO)from the automatic density control key 222. When the editorcommunication grant key 206 is depressed on the control panel 140D, itis checked at step S02 if there is a command signal supplied from any ofthe keys "F1" to "F7" on the editor module 200C. In the absence detectedof any command signal supplied from the control panel 140D or the editormodule 200D, the central processing unit 172 repeats the step S02 untilit is found that there is any command signal S_(CMD) received from thecontrol panel 140D.

The central processing unit 172 proceeds to step S03 and executes a modeshift subroutine program if it is detected at step S02 that there is thesignal from the image scale-up or scale-down key 148 or 150, the signalfrom the sheet size select key 154 or 156, the density step-up orstep-down signal S_(D+) or S_(D-) from the manual density "plus" or"minus" key 164 or 166, or the automatic density control mode selectsignal S_(AUTO). Responsive to any of these signals supplied from thecontrol panel 140D, the central processing unit 172 executes the stepsrequired by the supplied signal on condition that the mode of operationrequested by the signal is validly acceptable in the apparatus. Thedetails of this mode shift subroutine program S03 will be hereinafterdescribed with reference to FIG. 61.

On the other hand, if it is detected at step S02 that there is a commandsignal supplied from any of the keys "F1" to "F7" on the editor module200C, the central processing unit 172 proceeds to subroutine program S04and executes an area attribute designation control subroutine program.The central processing unit 172 is enabled to execute this areaattribute designation control subroutine program S04 when, and onlywhen, the editor communication grant key 206 on the control panel 140Dis depressed to grant transmission of data and command signals from theeditor module 200 to the central processing unit 172. The details of thearea attribute designation control subroutine program S04 willhereinafter described with reference to FIG. 62.

If it is detected at step S02 that there is the signal supplied from thescan start key 142 on the control panel 140D, the central processingunit 172 proceeds to subroutine program S05 and executes a preliminaryscan control subroutine program. The details of this image read controlsubroutine program S05 will be hereinafter described with reference toFIGS. 63A and 63B. The central processing unit 172 then proceeds tosubroutine program S06 and executes an image read control subroutineprogram. The details of this image read control subroutine program S06are shown in FIGS. 64A and 64B.

FIG. 61 shows the details of the mode shift subroutine program S03included in the routine program hereinbefore described with reference toFIG. 60.

The mode shift subroutine program S03 starts with step T01 to check ifthe mode of operation requested by the command signal received from thecontrol panel 140D is validly acceptable in the apparatus and/or theexternal printer unit. If the answer for this step T01 is given in theaffirmative, the central processing unit 172 proceeds to step T02 toselect the requested mode of operation and thereafter reverts to themain routine program described with reference to FIG. 60 to check if anyother command signal is received from the control panel 140B or from theeditor module 200D. If it is determined at step T01 that the mode ofoperation requested by the command signal received from the controlpanel 140D is not validly acceptable and accordingly the answer for stepT01 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 60 to check if any other command signal is received from thecontrol panel 140D or from the editor module 200D.

The request for a mode of operation to be checked for at step T01 may bea request for any size of print output sheets from the sheet size selectkey 154 or 156, a request for the change of the reduction/magnificationratio from the image scale-up or scale-down key 148 or 150, or a requestfor the change of the density for image reading from the density "plus"or "minus" key 164 or 166 on the control panel 140D, or a request forthe automatic density control mode from the automatic density controlmode select key 222 on the control panel 140D. When the editorcommunication grant key 206 is depressed on the control panel 140D, itmay be further checked at step T01 if there is a command signal suppliedfrom any of the keys "F1" to "F7" on the editor module 200D, a requestfor the change of the density for image reading from the density "plus"or "minus" key 216 or 218, and a request for the selection of theautomatic density control mode from the automatic density control modeselect key 240 on the editor module 200D.

In the absence detected of any command signal supplied from the controlpanel 140D or the editor module 200D, the central processing unit 172repeats the step T01 until it is found that there is any command signalS_(CMD) received from the control panel 140D.

FIG. 62 shows the details of the attribute designation controlsubroutine program S04 also included in the main routine programhereinbefore described with reference to FIG. 60.

The attribute designation control subroutine program S04 starts withstep U01 to check if the attribute of image reading operation asrequested by the command signal received from the editor module 200D isvalidly acceptable in the apparatus and/or the external printer unit. Ifthe answer for this step U01 is given in the affirmative, the centralprocessing unit 172 proceeds to step U02 to select the requestedattribute of image reading operation and stores the data representativeof the selected attribute into the attribute memory 212 in the controlcircuit 170F described with reference to FIG. 59. The central processingunit 172 thereafter reverts to the main routine program described withreference to FIG. 60 to check if any other command signal is receivedfrom the control panel 140D or from the editor module 200D.

If it is determined at step U01 that the attribute of image readingoperation requested by the command signal received from the editormodule 200D is not validly acceptable and accordingly the answer forstep U01 is given in the negative, the central processing unit 172immediately reverts to the main routine program described with referenceto FIG. 60 to check if any other command signal is received from thecontrol panel 140D or from the editor module 200D.

The attribute of image reading operation to be checked for at step U01may be the whiting or blackening of the image outside or inside aspecified local area or the selection of the automatic density controlmode, as indicated by the bit d₁ or d₀ of the attribute signal S_(ATT).

FIGS. 63A and 63B are flowcharts showing the details of the preliminaryscan control subroutine program S05 included in the main routine programhereinbefore described with reference to FIG. 60. As has been noted, thecentral processing unit 172 supplies the standard reference voltagesignals to the analog-to-digital converter 186 during execution thepreliminary scan control subroutine program.

As shown in FIGS. 63A and 63B, the preliminary scan control subroutineprogram S05 comprises steps V01 to V18, of which the steps V01 to V09are similar to the steps P01 to P09, respectively, of the preliminaryscan control ss hereinbefore described with reference to FIGS. 32A and32B in respect of the fourth preferred embodiment of the presentinvention.

When it is thus determined at step V09 that the document D on thedocument support table 102 is scanned at its leading end and accordinglythe answer for the step V09 turns affirmative, the central processingunit 172 proceeds to step V10 (FIG. 63B) at which the shaded digitalimage density data signals S_(SDD) supplied from the shading circuit 188and representing the original densities of the pixels forming the imageon the document D are loaded into the line memory 176 for each of thelines of pixels. The central processing unit 172 then proceeds to stepV11 to store into the internal memory (not shown) of the centralprocessing unit 172 the attribute data fetched from the attribute memory212 and selected for the pixels forming the designated local area "A1"or "A2" of the document D for which the automatic density control modeis selected. Subsequently to step V11, the central processing unit 172proceeds to step V12 to check if the shaded digital image density datasignals S_(SDD) supplied from the shading circuit 188 have been loadedinto the line memory 176 for all the lines of pixels.

When the answer for this step V12 is given in the affirmative, thecentral processing unit 172 proceeds to step V13 to detect whether ornot the lamp/mirror carrier 118 and mirror carrier 120 have reached thepositions effective to scan the trailing end of the document D on thedocument support table 102. The step V13 is repeated until it isconfirmed that the document D on the document support table 102 has beenscanned to its trailing end. Thus, the shaded digital image density datasignals S_(SDD) are loaded into the internal memory of the centralprocessing unit 172 successively for the individual scanning lines untilall the image on the document or in the designated local area of thedocument are scanned.

When it is thus determined at step V13 that the scanning of the documentD on the document support table 102 is complete and accordingly theanswer for the step V13 turns affirmative, the central processing unit172 proceeds to step V14 to cease the supply of the control signalS_(EXP) to the voltage regulator circuit 184 to de-activate the exposurelamp 106. The step V14 is followed by step V15 at which the centralprocessing unit 172 supplies the motor actuation signal S_(MD1) to themotor driver circuit 178 for the scanner drive motor 132. Responsive tothe motor actuation signal S_(MD1) thus received from the centralprocessing unit 172, the motor driver circuit 178 actuates the scannerdrive motor 132 into operation to move the lamp/mirror and mirrorcarriers 118 and 120 toward their home positions in the directionsindicated by arrowheads a' and b' in FIG. 1.

The central processing unit 172 then detects at step V16 whether or notthe lamp/mirror and mirror carriers 118 and 120 have reached theirrespective home positions. The step V16 is repeated until it isconfirmed that the lamp/mirror and mirror carriers 118 and 120 havereached their respective home positions. When it is thus found at stepV16 that the carriers 118 and 120 have reached their respective homepositions and accordingly the answer for the step V16 turns affirmative,the central processing unit 172 proceeds to step V17 to reset the signalS_(MD1) and stop the scanner drive motor 132.

Thereupon, the central processing unit 172 proceeds to step V18 to fetchthe data representative of the attribute data stored in the internalmemory of the central processing unit 172 (step V10) and calculate theoptimum threshold value for the image reading operation using theselected attributes for the designated local area "A1" or "A2" of thedocument D. On termination of the step V18, the central processing unit172 reverts to the main routine program illustrated in FIG. 60 and mayexecute the regular scan control subroutine program S06.

FIGS. 64A and 64B are flowcharts showing the details of the regular scancontrol subroutine program S06. The steps W01 to W17 of the regular scancontrol subroutine program S06 to be executed by the central processingunit 172 in the sixth preferred embodiment of the present invention areentirely similar to the steps Q01 to Q16 of the ss hereinbeforedescribed with reference to FIGS. 33A and 33B in regard to the fourthpreferred embodiment of the present invention and, as such, will not beherein described.

Seventh Preferred Embodiment (FIGS. 65, 66A and 66B)

While the sixth preferred embodiment of the present invention is adaptedto carry out the image reading operation exclusively in the simplebinarization mode, such an embodiment of the present invention may bereadily modified. FIG. 65 illustrates the control circuit 170G includedin such a modified embodiment of the present invention.

In the control circuit 170G shown in FIG. 65, there is provided ahalftone threshold generator circuit 242 in addition to the circuitelements forming the control circuit 170F described with reference toFIG. 59. The halftone threshold generator circuit 242 is responsive to ahalftone image-density signal S_(HD) supplied from the centralprocessing unit 172 to generate a signal S_(HT) representative of theoptimum threshold values or the dither pattern for the halftone mode ofimage reading operation on the basis of the image density represented bythe halftone image-density signal S_(HD).

FIGS. 66A and 66B are flowcharts showing the details of the preliminaryscan control subroutine program included in the main routine program tobe executed by the central processing unit 172 in the seventh preferredembodiment of the present invention. The preliminary scan controlsubroutine program herein shown comprises steps X01 to X18, of which thesteps X01 to X17 are similar to the steps V01 to V17, respectively, ofthe preliminary scan control ss hereinbefore described with reference toFIGS. 63A and 63B in respect of the fourth preferred embodiment of thepresent invention.

After the scanner drive motor 132 is brought to a stop at step X17, thecentral processing unit 172 proceeds to step X18 to fetch the datarepresentative of the attribute data stored in the internal memory ofthe central processing unit 172 (step X10) and calculate the optimum setof threshold values, that is, the optimum dither pattern for the imagereading operation using the selected attributes for the designated localarea "A1" or "A2" of the document D. On termination of the step X18, thecentral processing unit 172 reverts to the main routine program and mayexecute the regular scan control subroutine program which is alsosimilar to the ss described with reference to FIGS. 33A and 33B.

What is claimed is:
 1. An image reading apparatus comprising:a) imagereading means for optically reading images on a document and forgenerating electric signals representative of the optically read images,b) area designating means for designating a plurality of local areas ofsaid document, c) density designating means for designating the densitylevel of the image to be reproduced from each of the designated localareas of the document independently of the density level of other areas,and d) control means for controlling said image reading means so thatthe images in the designated local areas of the document are to bereproduced with densities based on the density levels designated foreach of the local areas.
 2. An apparatus as set forth in claim 1,wherein said area designating means comprises a support means forsupporting said document, and pen means for designating particularpoints corresponding to the local areas on the support means.
 3. Anapparatus as set forth in claim 1, wherein said density designatingmeans comprises a plurality of keys.
 4. An apparatus as set forth inclaim 1, further comprising means for indicating the density levelsdesignated by said density designating means.
 5. An image dataprocessing apparatus for processing image data comprising:a) areadesignating means for designating a plurality of local areas of an imageto be reproduced, b) density designating means for designating densitylevels of images corresponding to the designated local areas wherein thedensity level of the image corresponding to each of the local areas isindividually designated, c) data processing means for processing theimage data corresponding to said images to be reproduced and outputtingthe same, and d) control means for controlling said data processingmeans so that the images in the designated local areas are to bereproduced with the densities based on the density levels which aredesignated for each of the local areas.
 6. An apparatus as set forth inclaim 5, wherein said area designating means comprises a support meansfor supporting said document, and pen means for designating particularpoints corresponding to the local areas on the support means.
 7. Anapparatus as set forth in claim 5, wherein said density designatingmeans comprises a plurality of keys.
 8. An apparatus as set forth inclaim 5, further comprising indicating means for indicating the densitylevels designated by said density designating means.
 9. An imageprocessing apparatus for processing an image data comprising:areadesignating means for designating a plurality of local areas of an imagecorresponding to the image data to be processed; density designatingmeans for designating individual density levels corresponding to each ofthe designated local areas; generating means for generating a thresholdvalue corresponding to each of the density levels designated by saiddensity designating means; and data processing means for comparing theimage data corresponding to each of the local areas with thecorresponding threshold value generated by said generating means and foroutputting processed image data according to results of the comparison.10. An image processing apparatus for processing an image datacomprising:area designating means for designating a plurality of localareas of an image corresponding to the image data to be processed;selecting means for selecting one or more reference values correspondingto each of the plurality of local areas designated by said areadesignating means, said reference values corresponding to each of thelocal areas being selected independently of each other; and comparingmeans for comparing the image data corresponding to each of the localareas with selected reference values corresponding to the same localarea and for outputting processed image data based on results of thecomparison.
 11. An image processing apparatus for processing an imagedata comprising:area designating means for designating a plurality oflocal areas of an image corresponding to the image data to be processed;density designating means for designating individual density levelscorresponding to each of the designated local areas; generating meansfor generating a plurality of threshold values including one or morestandard threshold values and local threshold values which correspond toeach of the designated local areas, generating each of the localthreshold values according to the corresponding density level designatedby said density designating means; and data processing means forcomparing the image data corresponding to each of the local areas withthe corresponding local threshold value, for comparing the image datacorresponding to an area which is out of the local areas with thestandard threshold values, and for outputting processed image dataaccording to results of the comparison.